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Magnetochemistry, Volume 9, Issue 7 (July 2023) – 30 articles

Cover Story (view full-size image): Single-component molecular conductor and Dirac electron system are both fascinating materials, but initially, they were thought to belong to different material categories. It was a big surprise that a Fermi surface was observed in the single-component molecular crystal [Ni(tmdt)2] at the beginning of this century, because the concept of a metal seems incompatible with the concept of a molecule. On the other hand, the energy band structure of the Dirac electron system possesses a unique feature known as the Dirac cone that consists of two conical surfaces with linear dispersion meeting at a single point in momentum space. We demonstrate that the single-component molecular crystal is suitable for the formation of the Dirac cone using tight-binding models and DFT calculations. View this paper
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17 pages, 6147 KiB  
Perspective
Lanthanide-Based Metal–Organic Frameworks with Single-Molecule Magnet Properties
Magnetochemistry 2023, 9(7), 190; https://doi.org/10.3390/magnetochemistry9070190 - 22 Jul 2023
Cited by 1 | Viewed by 1290
Abstract
Lanthanide metal–organic frameworks (Ln-MOFs) showing single-molecule magnet (SMM) properties are an ever-growing family of materials where the magnetic properties can be tuned by various interrelated parameters, such as the coordinated solvent, temperature, organic linkers, lanthanide ions and their coordination environment. An overview of [...] Read more.
Lanthanide metal–organic frameworks (Ln-MOFs) showing single-molecule magnet (SMM) properties are an ever-growing family of materials where the magnetic properties can be tuned by various interrelated parameters, such as the coordinated solvent, temperature, organic linkers, lanthanide ions and their coordination environment. An overview of the general synthetic methodologies to access MOFs/Ln-MOFs and the peculiarities and parameters to control and/or fine-tune their SMM behavior is herein presented. Additionally, diverse challenging strategies for inducing SMM/SIM behavior in an Ln-MOF are discussed, involving redox activity and chirality. Furthermore, intriguing physical phenomena such as the CISS effect and CPL are also highlighted. Full article
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19 pages, 4980 KiB  
Article
Enhanced Energy Recovery in Magnetic Energy-Harvesting Shock Absorbers Using Soft Magnetic Materials
Magnetochemistry 2023, 9(7), 189; https://doi.org/10.3390/magnetochemistry9070189 - 20 Jul 2023
Viewed by 1016
Abstract
In the automobile sector, energy recovery and sustainability are becoming more and more important, and energy-harvesting suspension systems (EHSAs) have a lot of promise to improve vehicle efficiency. This investigation expands on prior work that investigated the viability of an EHSA that uses [...] Read more.
In the automobile sector, energy recovery and sustainability are becoming more and more important, and energy-harvesting suspension systems (EHSAs) have a lot of promise to improve vehicle efficiency. This investigation expands on prior work that investigated the viability of an EHSA that uses permanent magnets and amorphous core coils. The performance of the proposed system is demonstrated and enhanced in the current study through the development and optimization of a prototype. A thorough testing of the prototype is performed to determine design improvements for boosting the system’s overall performance and to quantify the recovered energy. In previous work, a method was proposed to find the dependence of the magnetic flux with the relative position between the primary and secondary elements to obtain the optimal position for the system. This method is applied to optimize the energy harvesting coil by testing different configurations in terms of the placement and type of amorphous or nonamorphous core inside the energy harvesting coil. This is a crucial area of attention in order to maximize energy recovery while solving the low-frequency problem that suspension systems have (on the order of 10 Hz). Full article
(This article belongs to the Special Issue Magnetism: Energy, Recycling, Novel Materials)
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17 pages, 4990 KiB  
Article
Enhanced Magnetic Cooling through Tailoring the Size-Dependent Magnetocaloric Effect of Iron Nanoparticles Embedded in Titanium Nitride Thin Films
Magnetochemistry 2023, 9(7), 188; https://doi.org/10.3390/magnetochemistry9070188 - 19 Jul 2023
Viewed by 1227
Abstract
The magnetocaloric effect (MCE) in iron (Fe) nanoparticles incorporated within a titanium nitride (TiN) thin-film matrix grown using pulsed laser deposition (PLD) is investigated in this study. The study demonstrates the ability to control the entropy change across the magnetic phase transition by [...] Read more.
The magnetocaloric effect (MCE) in iron (Fe) nanoparticles incorporated within a titanium nitride (TiN) thin-film matrix grown using pulsed laser deposition (PLD) is investigated in this study. The study demonstrates the ability to control the entropy change across the magnetic phase transition by varying the size of the Fe nanoparticles. The structural characterization carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning transmission electron (TEM) showed that TiN films are (111) textured, while the Fe-particles are mostly spherical in shapes, are single-crystalline, and have a coherent structure with the surrounding TiN thin-film matrix. The TiN thin-film matrix was chosen as a spacer layer since it is nonmagnetic, is highly corrosion-resistive, and can serve as an excellent conduit for extracting heat due to its high thermal conductivity (11 W/m K). The magnetic properties of Fe–TiN systems were investigated using a superconducting quantum interference device (SQUID) magnetometer. In-plane magnetic fields were applied to record magnetization versus field (M–H) and magnetization versus temperature (M–T) curves. The results showed that the Fe–TiN heterostructure system exhibits a substantial isothermal entropy change (ΔS) over a wide temperature range, encompassing room temperature to the blocking temperature of the Fe nanoparticles. Using Maxwell’s relation and analyzing magnetization–temperature data under different magnetic fields, quantitative insights into the isothermal entropy change (ΔS) and magnetocaloric effect (MCE) were obtained for the Fe–TiN heterostructure system. The study points out a considerable negative change in ΔS that reaches up to 0.2 J/kg K at 0.2 T and 300 K for the samples with a nanoparticle size on the order of 7 nm. Comparative analysis revealed that Fe nanoparticle samples demonstrate higher refrigeration capacity (RC) in comparison to Fe thin-film multilayer samples, with the RC increasing as the Fe particle size decreases. These findings provide valuable insights into the potential application of Fe–TiN heterostructures in solid-state cooling technologies, highlighting their enhanced magnetocaloric properties. Full article
(This article belongs to the Special Issue Latest Advancements in Functional Magnetic Nanostructures)
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16 pages, 5220 KiB  
Article
Electrospun PCL/PVA Coaxial Nanofibers with Embedded Titanium Dioxide and Magnetic Nanoparticles for Stabilization and Controlled Release of Dithranol for Therapy of Psoriasis
Magnetochemistry 2023, 9(7), 187; https://doi.org/10.3390/magnetochemistry9070187 - 19 Jul 2023
Cited by 1 | Viewed by 972
Abstract
Dithranol is one of the oldest and most efficient drugs used in the treatment of psoriasis. One of the challenges with using dithranol is its photostability, because it easily degrades when exposed to light. This study investigated the potential of coaxial core-sheath PCL/PVA [...] Read more.
Dithranol is one of the oldest and most efficient drugs used in the treatment of psoriasis. One of the challenges with using dithranol is its photostability, because it easily degrades when exposed to light. This study investigated the potential of coaxial core-sheath PCL/PVA nanofibers as a dual-functional system for enhancing dithranol photostability and remote-controlled drug delivery for psoriasis therapy. We have shown that coaxial nanofibers with titanium oxide nanoparticles (reflecting and absorbing ultra-violet light) in the PVA-based sheath part of the nanofibers can increase dithranol photostability. Incorporation of dithranol and magnetic nanoparticles into a PCL-based core of the nanofibers enables dithranol release control via an external radio-frequency field. The application of a radio-frequency field generates heat that can be used to control the release rate of drugs. Our approach therefore offers a non-invasive and remotely controlled drug release system that hold promise for the development of new topical formulations for psoriasis treatment using dithranol. Full article
(This article belongs to the Section Applications of Magnetism and Magnetic Materials)
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11 pages, 6366 KiB  
Article
Femtosecond Laser Ablation-Induced Magnetic Phase Transformations in FeRh Thin Films
Magnetochemistry 2023, 9(7), 186; https://doi.org/10.3390/magnetochemistry9070186 - 18 Jul 2023
Viewed by 1025
Abstract
In this study, we present a novel investigation into the magnetic and morphological properties of equiatomic B2-ordered FeRh thin films irradiated with single high-intensity ultrashort laser pulses. The goal is to elucidate the effect of femtosecond laser ablation on the magnetic properties of [...] Read more.
In this study, we present a novel investigation into the magnetic and morphological properties of equiatomic B2-ordered FeRh thin films irradiated with single high-intensity ultrashort laser pulses. The goal is to elucidate the effect of femtosecond laser ablation on the magnetic properties of FeRh. We employed Scanning Magneto-Optical Kerr Effect (S-MOKE) microscopy to examine the magnetic phase after laser processing, providing high spatial resolution and sensitivity. Our results for the first time demonstrated the appearance of a magneto-optical signal from the bottom of ablation craters, suggesting a transition from antiferromagnetic to ferromagnetic behavior. Fluence-resolved measurements clearly demonstrate that the ablation threshold coincides with the threshold of the antiferromagnet-to-ferromagnet phase transition. The existence of such a magnetic phase transition was independently confirmed by temperature-dependent S-MOKE measurements using a CW laser as a localized heat source. Whereas the initial FeRh film displayed a reversible antiferromagnet-ferromagnet phase transition, the laser-ablated structures exhibited irreversible changes in their magnetic properties. This comprehensive analysis revealed the strong correlation between the femtosecond laser ablation process and the magnetic phase transformation in FeRh thin films. Full article
(This article belongs to the Special Issue State-of-the-Art Research in Magnetism in France)
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17 pages, 1977 KiB  
Article
Effect of Electron Correlations on the Electronic Structure and Magnetic Properties of the Full Heusler Alloy Mn2NiAl
Magnetochemistry 2023, 9(7), 185; https://doi.org/10.3390/magnetochemistry9070185 - 17 Jul 2023
Cited by 3 | Viewed by 836
Abstract
In this theoretical study, we investigate the effect of electron correlations on the electronic structure and magnetic properties of the full Heusler alloy Mn2NiAl in the framework of first-principles calculations. We investigate the electron correlation effect as employed within hybrid functional [...] Read more.
In this theoretical study, we investigate the effect of electron correlations on the electronic structure and magnetic properties of the full Heusler alloy Mn2NiAl in the framework of first-principles calculations. We investigate the electron correlation effect as employed within hybrid functional (HSE) and also within the DFT+U method with varied values of parameters between 0.9 and 6 eV. The XA-crystal structure was investigated with antiferromagnetic orderings of the magnetic moments of the manganese. It was found that with a growth of the Coulomb interaction parameter, the manganese ions magnetic moment increases, and it reaches the value of 4.15–4.46 μB per Mn. In addition, the total magnetic moment decreases because of the AFM ordering of the Mn ions and a small magnetic moment of Ni. The calculated total magnetic value agrees well with recent experiments demonstrating a low value of magnetization. This experimental value is most closely reproduced for the moderate values of the Coulomb parameter, also calculated in constrained LDA, while previous DFT studies substantially overestimated this value. It is also worth noticing that for all values of the Coulomb interaction parameter, this compound remains metallic in its electronic structure in agreement with transport measurements. Full article
(This article belongs to the Special Issue Magnetic Properties of Metals and Alloys)
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13 pages, 2569 KiB  
Article
Towards Resonantly Enhanced Acoustic Phonon-Exchange Magnon Interactions at THz Frequencies
Magnetochemistry 2023, 9(7), 184; https://doi.org/10.3390/magnetochemistry9070184 - 17 Jul 2023
Cited by 2 | Viewed by 957
Abstract
Using valid experimental parameters, we quantify the magnitude of resonantly phonon-driven precession of exchange magnons in freestanding ferromagnetic nickel thin films on their thickness L. Analytical solutions of acoustically driven equations for magnon oscillators display a nonmonotonous dependence of the peak magnetization [...] Read more.
Using valid experimental parameters, we quantify the magnitude of resonantly phonon-driven precession of exchange magnons in freestanding ferromagnetic nickel thin films on their thickness L. Analytical solutions of acoustically driven equations for magnon oscillators display a nonmonotonous dependence of the peak magnetization precession on the film thickness. It is explained by different L-dependence of multiple prefactors entering in the expression for the total magnetization dynamics. Depending on the ratio of acoustic and magnetic (Gilbert) damping constants, the magnetization precession is shown to be amplified by a Q-factor of either the phonon or the magnon resonance. The increase in the phonon mode amplitude for thinner membranes is also found to be significant. Focusing on the magnetization dynamics excited by the two first acoustic eigenmodes with p=1 and p=2, we predict the optimum thicknesses of nickel membranes to achieve large amplitude magnetization precession at multi 100 GHz frequencies at reasonably low values of an external magnetic field. By extending the study to the case of Ni-Si bilayers, we show that these resonances are achievable at even higher frequencies, approaching the THz range. Full article
(This article belongs to the Special Issue State-of-the-Art Research in Magnetism in France)
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19 pages, 3073 KiB  
Article
Electrically Detected Magnetic Resonance on a Chip (EDMRoC) for Analysis of Thin-Film Silicon Photovoltaics
Magnetochemistry 2023, 9(7), 183; https://doi.org/10.3390/magnetochemistry9070183 - 15 Jul 2023
Viewed by 1160
Abstract
Electrically detected magnetic resonance (EDMR) is a spectroscopic technique that provides information about the physical properties of materials through the detection of variations in conductivity induced by spin-dependent processes. EDMR has been widely applied to investigate thin-film semiconductor materials in which the presence [...] Read more.
Electrically detected magnetic resonance (EDMR) is a spectroscopic technique that provides information about the physical properties of materials through the detection of variations in conductivity induced by spin-dependent processes. EDMR has been widely applied to investigate thin-film semiconductor materials in which the presence of defects can induce the current limiting processes. Conventional EDMR measurements are performed on samples with a special geometry that allows the use of a typical electron paramagnetic resonance (EPR) resonator. For such measurements, it is of utmost importance that the geometry of the sample under assessment does not influence the results of the experiment. Here, we present a single-board EPR spectrometer using a chip-integrated, voltage-controlled oscillator (VCO) array as a planar microwave source, whose geometry optimally matches that of a standard EDMR sample, and which greatly facilitates electrical interfacing to the device under assessment. The probehead combined an ultrasensitive transimpedance amplifier (TIA) with a twelve-coil array, VCO-based, single-board EPR spectrometer to permit EDMR-on-a-Chip (EDMRoC) investigations. EDMRoC measurements were performed at room temperature on a thin-film hydrogenated amorphous silicon (a-Si:H) pin solar cell under dark and forward bias conditions, and the recombination current driven by the a-Si:H dangling bonds (db) was detected. These experiments serve as a proof of concept for a new generation of small and versatile spectrometers that allow in situ and operando EDMR experiments. Full article
(This article belongs to the Special Issue Magnetic Materials, Thin Films and Nanostructures (Volume II))
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10 pages, 3890 KiB  
Article
Synthesis and Structural and Magnetic Properties of Polycrystalline GaMo4Se8
Magnetochemistry 2023, 9(7), 182; https://doi.org/10.3390/magnetochemistry9070182 - 12 Jul 2023
Viewed by 737
Abstract
GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). [...] Read more.
GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). In this work, we have obtained pure GaMo4Se8 in polycrystalline form through an innovative two-step synthetic route. Phase purity and chemical composition were confirmed through the Rietveld refinement of the powder XRD pattern, the sample characterisation having been complemented with SEM analysis. The magnetic phase diagram was investigated using DC (VSM) and AC magnetometry, which disclosed the presence of cycloidal, skyrmionic and ferromagnetic phases in polycrystalline GaMo4Se8. Full article
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10 pages, 4551 KiB  
Article
Effect of Cr3+ Doping on Magnetic Properties of Zn-Mg Ferrite Nanoparticles
Magnetochemistry 2023, 9(7), 181; https://doi.org/10.3390/magnetochemistry9070181 - 11 Jul 2023
Viewed by 887
Abstract
Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were synthesized using a hydrothermal technique. The obtained magnetic nanoparticles (MNPs) exhibited a spinel structure, where the lattice constant decreased with the Cr3+ ion content. The [...] Read more.
Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were synthesized using a hydrothermal technique. The obtained magnetic nanoparticles (MNPs) exhibited a spinel structure, where the lattice constant decreased with the Cr3+ ion content. The doping of Cr3+ ion (x = 0.1) increased the specific saturation magnetization to 46.4 emu/g but decreased to 20.0 emu/g with the further increase in the Cr3+ ion content to x = 0.4. The decrement in Curie temperature was ascribed to the weakened super-exchange interaction between the metal ions located at A-sites and B-sites, which arose from the doping of the Cr3+ ion. The T2-weighted images gradually darkened with the increase in Zn0.6Mg0.4Cr0.1Fe1.9O4 nanoparticles concentration, suggesting that the nanoparticles can enhance the image contrast. Zn0.6Mg0.4CrxFe2−xO4 (0 ≤ x ≤ 0.4) nanoparticles were able to heat the agar phantom to the hyperthermia temperature under the safe alternating magnetic field, which showed their potential in the magnetic induction hyperthermia. Full article
(This article belongs to the Special Issue Advances in Magnetic Microspheres)
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9 pages, 1596 KiB  
Communication
Nonthermal Equilibrium Process of Charge Carrier Extraction in Metal/Insulator/Organic Semiconductor/Metal (MIOM) Junction
Magnetochemistry 2023, 9(7), 180; https://doi.org/10.3390/magnetochemistry9070180 - 11 Jul 2023
Viewed by 725
Abstract
This paper presents the concept and experimental evidence for the nonthermal equilibrium (NTE) process of charge carrier extraction in metal/insulator/organic semiconductor/metal (MIOM) capacitors. These capacitors are structurally similar to metal/insulator/semiconductor/(metal) (MIS) capacitors found in standard semiconductor textbooks. The difference between the two capacitors [...] Read more.
This paper presents the concept and experimental evidence for the nonthermal equilibrium (NTE) process of charge carrier extraction in metal/insulator/organic semiconductor/metal (MIOM) capacitors. These capacitors are structurally similar to metal/insulator/semiconductor/(metal) (MIS) capacitors found in standard semiconductor textbooks. The difference between the two capacitors is that the (organic) semiconductor/metal contacts in the MIOM capacitors are of the Schottky type, whereas the contacts in the MIS capacitors are of the ohmic type. Moreover, the mobilities of most organic semiconductors are significantly lower than those of inorganic semiconductors. As the MIOM structure is identical to the electrode portion of an organic field-effect transistor (OFET) with top-contact and bottom-gate electrodes, the hysteretic behavior of the OFET transfer characteristics can be deduced from the NTE phenomenon observed in MIOM capacitors. Full article
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4 pages, 207 KiB  
Editorial
Special Issue: Soft and Hard Magnetic Materials: Latest Advances and Prospects
Magnetochemistry 2023, 9(7), 179; https://doi.org/10.3390/magnetochemistry9070179 - 10 Jul 2023
Viewed by 999
Abstract
The Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects aims to provide researchers with an overview of some aspects of the current research in magnetic materials from theoretical studies to their applications, including their fabrication and characterization [...] Full article
(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)
14 pages, 4443 KiB  
Article
Homoconjugation Mediated Spin-Spin Coupling in Triptycene Nitronyl Nitroxide Diradicals
Magnetochemistry 2023, 9(7), 178; https://doi.org/10.3390/magnetochemistry9070178 - 09 Jul 2023
Viewed by 1054
Abstract
In contrast to diradical linked by π-conjugation, there have been only a limited number of studies reported for those linked by homoconjugation systems. Bis(nitronyl nitroxide) diradicals and monoradical connected by a core non-rigid triptycene unit were synthesized. EPR spectroscopy and SQUID were employed [...] Read more.
In contrast to diradical linked by π-conjugation, there have been only a limited number of studies reported for those linked by homoconjugation systems. Bis(nitronyl nitroxide) diradicals and monoradical connected by a core non-rigid triptycene unit were synthesized. EPR spectroscopy and SQUID were employed to investigate the magnetic exchange interactions. The results demonstrate that the values of ΔEST are 0.19 kcal/mol (J = 34.4 cm−1) for 2,6-TP-NN and −0.21 kcal/mol (J = −36.9 cm−1) for 2,7-TP-NN, indicating ferromagnetic interaction and antiferromagnetic interaction, respectively. The spin polarization rule is not a precise predictor of the behavior of triptycene diradicals, and therefore, we improve the model. The experimental findings indicate that homoconjugation can function directly as a coupling pathway between the two spin centers, which is in qualitative agreement with the DFT theoretical calculations and the Borden rule. This research has found a special means of achieving spin coupling in non-rigid aromatics by means of homoconjugation. Full article
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19 pages, 8707 KiB  
Article
Characterization and Magnetic Properties of Sintered Glass-Ceramics from Dispersed Fly Ash Microspheres
Magnetochemistry 2023, 9(7), 177; https://doi.org/10.3390/magnetochemistry9070177 - 09 Jul 2023
Viewed by 1231
Abstract
The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with [...] Read more.
The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with a diameter smaller than 10 μm, which are anthropogenic atmospheric pollutants PM10. Due to their composition and fine-grained powder morphology, they can be converted into sintered products. In this study, dispersed microspheres from class C fly ash were directly sintered without any additive to form high-strength glass-ceramics with magnetic properties. The optimum processing conditions were achieved at a temperature of 1200 °C, at which samples with a compressive strength of 100.6 MPa were obtained. Sintering reduces the quantity of the glass phase and promotes the formation of larnite, Fe-spinel, ye’elimite, and ternesite. Mössbauer measurements show that the relative concentration of the magnetic phase compared to the paramagnetic one rises almost in order. The sintered sample demonstrates a narrower distribution of the hyperfine magnetic field and a significantly lower value of the coercive field of 25 Oe, which allows proposing such materials as soft magnetic materials. The presented results demonstrate promising industrial applications of hazardous PM10 to minimize solid waste pollution. Full article
(This article belongs to the Section Magnetic Materials)
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13 pages, 5182 KiB  
Article
Spacer Thickness and Temperature Dependences of the Interlayer Exchange Coupling in a Co/Pt/Co Three-Layer Structure
Magnetochemistry 2023, 9(7), 176; https://doi.org/10.3390/magnetochemistry9070176 - 08 Jul 2023
Viewed by 718
Abstract
Domain wall mobility as a function of nonmagnetic interlayer thickness and temperature was studied in ultrathin exchange-coupled ferromagnetic layers using magneto-optic Kerr microscopy. The system under study is a Pt/Co/Pt/Co/Pt heterostructure having perpendicular magnetic anisotropy and a middle Pt layer with spatially variable [...] Read more.
Domain wall mobility as a function of nonmagnetic interlayer thickness and temperature was studied in ultrathin exchange-coupled ferromagnetic layers using magneto-optic Kerr microscopy. The system under study is a Pt/Co/Pt/Co/Pt heterostructure having perpendicular magnetic anisotropy and a middle Pt layer with spatially variable thickness. The ferromagnetic interaction between the Co layers is observed when the Pt interlayer thickness varies from 5 to 6 nm in a temperature range of 200–300 K. There is a certain interval of Pt layer thickness where domain walls in both ferromagnetic layers move independently. Nonlinear dependence of the domain wall displacement on the applied field was measured. It is shown that an equilibrium position of the relaxed domain wall depends on field, temperature, and the nonmagnetic interlayer thickness. This position is determined by the energy balance: (i) domain wall displacement provided by the applied field, (ii) interlayer exchange interaction in the area swept by the domain wall, and (iii) domain wall coercivity. The mechanism of domain wall stabilization in terms of independent wall motion near critical thickness was considered. It is found that both the coercivity of the Co layer and the critical thickness decrease at higher temperature, while the interlayer exchange constant J is changed weakly. Full article
(This article belongs to the Special Issue Ferroic Materials: Properties and Applications)
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14 pages, 3227 KiB  
Article
Novel Linear Trinuclear CuII Compound with Trapped Chiral Hemiaminal Ligand: Magnetostructural Study
Magnetochemistry 2023, 9(7), 175; https://doi.org/10.3390/magnetochemistry9070175 - 06 Jul 2023
Viewed by 814
Abstract
A new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat [...] Read more.
A new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat cationic structure [Cu3(HL′)2(H2O)2]4+ with a Cu3 linear core reached by the double Cu-OR/NN-Cu triazole/alkoxo bridge of the hemiaminal molecule. The CuII spin carriers are antiferromagnetically coupled, presenting a spin doublet ground state (S = 1/2) with a magnetic coupling constant of −179 cm−1. Moreover, DTF calculations show that the planarity of the compound permits a sigma-type overlapping between the unpaired electrons of the spin carriers and the p-type orbitals of the coordinated N and O atoms producing an electronic delocalization through the bridging ligand responsible for the strong antiferromagnetic interactions observed experimentally. Full article
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19 pages, 22520 KiB  
Article
Dirac Cone Formation in Single-Component Molecular Conductors Based on Metal Dithiolene Complexes
Magnetochemistry 2023, 9(7), 174; https://doi.org/10.3390/magnetochemistry9070174 - 06 Jul 2023
Cited by 1 | Viewed by 936
Abstract
Single-component molecular conductors exhibit a strong connection to the Dirac electron system. The formation of Dirac cones in single-component molecular conductors relies on (1) the crossing of HOMO and LUMO bands and (2) the presence of nodes in the HOMO–LUMO couplings. In this [...] Read more.
Single-component molecular conductors exhibit a strong connection to the Dirac electron system. The formation of Dirac cones in single-component molecular conductors relies on (1) the crossing of HOMO and LUMO bands and (2) the presence of nodes in the HOMO–LUMO couplings. In this study, we investigated the possibility of Dirac cone formation in two single-component molecular conductors derived from nickel complexes with extended tetrathiafulvalenedithiolate ligands, [Ni(tmdt)2] and [Ni(btdt)2], using tight-biding models and first-principles density-functional theory (DFT) calculations. The tight-binding model predicts the emergence of Dirac cones in both systems, which is associated with the stretcher bond type molecular arrangement. The DFT calculations also indicate the formation of Dirac cones in both systems. In the case of [Ni(btdt)2], the DFT calculations, employing a vdW-DF2 functional, reveal the formation of Dirac cones near the Fermi level in the nonmagnetic state after structural optimization. Furthermore, the DFT calculations, by utilizing the range-separated hybrid functional, confirm the antiferromagnetic stability in [Ni(btdt)2], as observed experimentally. Full article
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16 pages, 1086 KiB  
Article
On the Size of Superconducting Islands on the Density-Wave Background in Organic Metals
Magnetochemistry 2023, 9(7), 173; https://doi.org/10.3390/magnetochemistry9070173 - 04 Jul 2023
Cited by 2 | Viewed by 708
Abstract
Most high-Tc superconductors are spatially inhomogeneous. Usually, this heterogeneity originates from the interplay of various types of electronic ordering. It affects various superconducting properties, such as the transition temperature, the magnetic upper critical field, the critical current, etc. In this paper, [...] Read more.
Most high-Tc superconductors are spatially inhomogeneous. Usually, this heterogeneity originates from the interplay of various types of electronic ordering. It affects various superconducting properties, such as the transition temperature, the magnetic upper critical field, the critical current, etc. In this paper, we analyze the parameters of spatial phase segregation during the first-order transition between superconductivity (SC) and a charge- or spin-density wave state in quasi-one-dimensional metals with imperfect nesting, typical of organic superconductors. An external pressure or another driving parameter increases the transfer integrals in electron dispersion, which only slightly affects SC but violates the Fermi surface nesting and suppresses the density wave (DW). At a critical pressure Pc, the transition from a DW to SC occurs. We estimate the characteristic size of superconducting islands during this phase transition in organic metals in two ways. Using the Ginzburg–Landau expansion, we analytically obtain a lower bound for the size of SC domains. To estimate a more specific interval of the possible size of the superconducting islands in (TMTSF)2PF6 samples, we perform numerical calculations of the percolation probability via SC domains and compare the results with experimental resistivity data. This helps to develop a consistent microscopic description of SC spatial heterogeneity in various organic superconductors. Full article
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19 pages, 13319 KiB  
Article
Assessment of a Computational Protocol for Predicting Co-59 NMR Chemical Shift
Magnetochemistry 2023, 9(7), 172; https://doi.org/10.3390/magnetochemistry9070172 - 02 Jul 2023
Viewed by 1259
Abstract
In the present study, we benchmark computational protocols for predicting Co-59 NMR chemical shift. Quantum mechanical calculations based on density functional theory were used, in conjunction with our NMR-DKH basis sets for all atoms, including Co, which were developed in the present study. [...] Read more.
In the present study, we benchmark computational protocols for predicting Co-59 NMR chemical shift. Quantum mechanical calculations based on density functional theory were used, in conjunction with our NMR-DKH basis sets for all atoms, including Co, which were developed in the present study. The best protocol included the geometry optimization at BLYP/def2-SVP/def2-SVP/IEF-PCM(UFF) and shielding constant calculation at GIAO-LC-ωPBE/NMR-DKH/IEF-PCM(UFF). This computational scheme was applied to a set of 34 Co(III) complexes, in which, Co-59 NMR chemical shift ranges from +1162 ppm to +15,100 ppm, and these were obtained in distinct solvents (water and organic solvents). The resulting mean absolute deviation (MAD), mean relative deviation (MRD), and coefficient of determination (R2) were 158 ppm, 3.0%, and 0.9966, respectively, suggesting an excellent alternative for studying Co-59 NMR. Full article
(This article belongs to the Special Issue NMR Spectroscopy in Transition Metal Complexes)
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15 pages, 1843 KiB  
Perspective
Prospects of Using Machine Learning and Diamond Nanosensing for High Sensitivity SARS-CoV-2 Diagnosis
Magnetochemistry 2023, 9(7), 171; https://doi.org/10.3390/magnetochemistry9070171 - 30 Jun 2023
Cited by 2 | Viewed by 1274
Abstract
The worldwide death toll claimed by Acute Respiratory Syndrome Coronavirus Disease 2019 (SARS-CoV), including its prevailed variants, is 6,812,785 (worldometer.com accessed on 14 March 2023). Rapid, reliable, cost-effective, and accurate diagnostic procedures are required to manage pandemics. In this regard, we bring attention [...] Read more.
The worldwide death toll claimed by Acute Respiratory Syndrome Coronavirus Disease 2019 (SARS-CoV), including its prevailed variants, is 6,812,785 (worldometer.com accessed on 14 March 2023). Rapid, reliable, cost-effective, and accurate diagnostic procedures are required to manage pandemics. In this regard, we bring attention to quantum spin magnetic resonance detection using fluorescent nanodiamonds for biosensing, ensuring the benefits of artificial intelligence-based biosensor design on an individual patient level for disease prediction and data interpretation. We compile the relevant literature regarding fluorescent nanodiamonds-based SARS-CoV-2 detection along with a short description of viral proliferation and incubation in the cells. We also propose a potentially effective strategy for artificial intelligence-enhanced SARS-CoV-2 biosensing. A concise overview of the implementation of artificial intelligence algorithms with diamond magnetic nanosensing is included, covering this roadmap’s benefits, challenges, and prospects. Some mutations are alpha, beta, gamma, delta, and Omicron with possible symptoms, viz. runny nose, fever, sore throat, diarrhea, and difficulty breathing accompanied by severe body pain. The recommended strategy would deliver reliable and improved diagnostics against possible threats due to SARS-CoV mutations, including possible pathogens in the future. Full article
(This article belongs to the Section Applications of Magnetism and Magnetic Materials)
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16 pages, 5462 KiB  
Article
Magnetic and Magnetocaloric Properties of Nano- and Polycrystalline Bulk Manganites La0.7Ba(0.3−x)CaxMnO3 (x ≤ 0.25)
Magnetochemistry 2023, 9(7), 170; https://doi.org/10.3390/magnetochemistry9070170 - 30 Jun 2023
Viewed by 1057
Abstract
Here we report the synthesis and investigation of bulk and nano-sized La0.7Ba0.3−xCaxMnO3 (x = 0, 0.15, 0.2 and 0.25) compounds that are promising candidates for magnetic refrigeration applications. We compare the structural and magnetic properties of [...] Read more.
Here we report the synthesis and investigation of bulk and nano-sized La0.7Ba0.3−xCaxMnO3 (x = 0, 0.15, 0.2 and 0.25) compounds that are promising candidates for magnetic refrigeration applications. We compare the structural and magnetic properties of bulk and nano-scale polycrystalline La0.7Ba0.3−xCaxMnO3 for potential use in magnetic cooling systems. Solid-state reactions were implemented for bulk materials, while the sol–gel method was used for nano-sized particles. Structurally and morphologically, the samples were investigated by X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). Oxygen stoichiometry was investigated by iodometry. Bulk compounds exhibit oxygen deficiency, while nano-sized particles show excess oxygen. Critical magnetic behavior was revealed for all samples using the modified Arrott plot (MAP) method and confirmed by the Kouvel–Fisher (KF) method. The bulk polycrystalline compound behavior was better described by the tricritical field model, while the nanocrystalline samples were governed by the mean-field model. Resistivity in bulk material showed a peak at a temperature Tp1 attributed to grain boundary conditions and at Tp2 associated with a Curie temperature of Tc. Parent polycrystalline sample La0.7Ba0.3MnO3 has Tc at 340 K. Substitution of x = 0.15 of Ca brings Tc to 308 K, and x = 0.2 brings it to 279 K. Nanocrystalline samples exhibit a very wide effective temperature range in the magnetocaloric effect, up to 100 K. Bulk compounds exhibit a high and sharp peak in magnetic entropy change, up to 7 J/kgK at 4 T at Tc for x = 0.25. To compare the magnetocaloric performances of the studied compounds, both relative cooling power (RCP) and temperature-averaged entropy change (TEC) figures of merit were used. RCP is comparable for bulk polycrystalline and nano-sized samples of the same substitution level, while TEC shows a large difference between the two systems. The combination of bulk and nanocrystalline materials can contribute to the effectiveness and improvement of magnetocaloric materials. Full article
(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)
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12 pages, 4905 KiB  
Article
Microstructure and Magnetic Property Evolution Induced by Heat Treatment in Fe-Si/SiO2 Soft Magnetic Composites
Magnetochemistry 2023, 9(7), 169; https://doi.org/10.3390/magnetochemistry9070169 - 29 Jun 2023
Viewed by 879
Abstract
SiO2 has been extensively studied as a superior insulating layer for innovative Fe-based soft magnetic composites (SMCs). During the preparation process of SMCs, appropriate heat treatment can effectively alleviate internal stress, reduce dislocation density, decrease coercivity, and enhance permeability. Maintaining the uniformity [...] Read more.
SiO2 has been extensively studied as a superior insulating layer for innovative Fe-based soft magnetic composites (SMCs). During the preparation process of SMCs, appropriate heat treatment can effectively alleviate internal stress, reduce dislocation density, decrease coercivity, and enhance permeability. Maintaining the uniformity and integrity of SiO2 insulating layers during heat treatment is a challenging task. Hence, it is crucial to explore the heat-treatment process and its effects on the magnetic properties of SMCs and their insulating layers. Herein, Fe–Si/SiO2 particles were prepared using chemical vapor deposition (CVD), and Fe–Si/SiO2 SMCs having a core–shell heterostructure were synthesized through hot-press sintering, and investigations were conducted into how heat-treatment temperature affected the microstructure of SMCs. This study thoroughly investigated the relationship between the evolution of SiO2 insulating layers and the magnetic properties. Additionally, the impact of the heat-treatment time on the magnetic properties of Fe-Si/SiO2 SMCs was evaluated. The results showed that in the temperature range of 823–923 K, the core–shell heterostructures grew more homogeneous and uniform. Concurrently, the stress and defects inside the Fe-Si/SiO2 SMCs were eliminated. When the temperature was raised over 973 K, the core–shell heterostructure was disrupted, and SiO2 began to disperse. After following a heat-treatment process (923 K) lasting up to 60 min, the resulting SMCs had high resistivity (1.04 mΩ·cm), the lowest hysteresis loss (P10 mt/100 kHz of 344.3 kW/m3), high saturation magnetization (191.2 emu/g). This study presents a new technique for producing SMCs using ceramic oxide as insulating layers. This study also includes a comprehensive analysis of the relationship between microstructure, magnetic properties, and heat treatment process parameters. These findings are crucial in expanding the potential applications of ceramic oxide. Full article
(This article belongs to the Special Issue Advances in Soft Magnetic Materials)
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15 pages, 5682 KiB  
Article
Magnetic Properties of CuCr1−xLaxS2 Thermoelectric Materials
Magnetochemistry 2023, 9(7), 168; https://doi.org/10.3390/magnetochemistry9070168 - 28 Jun 2023
Cited by 1 | Viewed by 636
Abstract
The magnetic properties (magnetic susceptibility, magnetic moment) and Weiss constant for lanthanum-doped CuCr1−xLaxS2 (x = 0; 0.005; 0.01; 0.015; 0.03) solid solutions were studied using static magnetochemistry at 80–750 K. The samples were characterized by both powder X-ray [...] Read more.
The magnetic properties (magnetic susceptibility, magnetic moment) and Weiss constant for lanthanum-doped CuCr1−xLaxS2 (x = 0; 0.005; 0.01; 0.015; 0.03) solid solutions were studied using static magnetochemistry at 80–750 K. The samples were characterized by both powder X-ray diffraction and energy-dispersive X-ray spectroscopy. It was shown that synthesized samples are single-phased up to x ≤ 0.01. The presence of the additional phase in the solid solutions with x > 0.015 caused deviation from the simple isovalent Cr3+→Ln3+ cationic substitution principle. It was found that magnetic susceptibility and the Weiss constant are significantly affected by both magnetic properties and lanthanum concentration for the solid solutions doped up to x = 0.01. The largest magnetic moment value of 3.88 µB was measured for the initial CuCrS2-matrix. The lowest value of 3.77 µB was measured for the CuCr0.99La0.01S2 solid solution. The lowest Weiss constant value of −147 K was observed for the initial matrix; the highest one was observed for CuCr0.99La0.01S2 (−139 K). The largest Seebeck coefficient value of 373 µV/K was measured for CuCr0.985La0.015S2 at 500 K; the obtained value was 3.3 times greater compared to the initial CuCrS2-matrix. The field dependence of the magnetic susceptibility allowed one to conclude the absence of ferromagnetic contributions in the total magnetic susceptibility of CuCr1−xLaxS2. The data on magnetic properties can be successfully utilized to investigate the limits of doping atom suitability and order–disorder phase transition temperature in CuCrS2-based solid solutions. Full article
(This article belongs to the Special Issue Magnetism: Energy, Recycling, Novel Materials)
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11 pages, 2729 KiB  
Article
Process-Gas-Influenced Anti-Site Disorder and Its Effects on Magnetic and Electronic Properties of Half-Metallic Sr2FeMoO6 Thin Films
Magnetochemistry 2023, 9(7), 167; https://doi.org/10.3390/magnetochemistry9070167 - 28 Jun 2023
Cited by 1 | Viewed by 1008
Abstract
Anti-site disorder, arising due to the similar size of Fe and Mo ions in Sr2FeMoO6 (SFMO) double perovskites, hampers spintronic applicability by deteriorating the magnetic response of this double perovskite system. A higher degree of anti-site disorder can also completely [...] Read more.
Anti-site disorder, arising due to the similar size of Fe and Mo ions in Sr2FeMoO6 (SFMO) double perovskites, hampers spintronic applicability by deteriorating the magnetic response of this double perovskite system. A higher degree of anti-site disorder can also completely destroy the half-metallicity of the SFMO system. To study the effects of different process gas conditions on the anti-site disorder, we have prepared a series of SFMO thin films on SrTiO3 (001) single-crystal substrate using a pulsed laser deposition (PLD) technique. The films are grown either under vacuum or under N2/O2 partial gas pressures. The vacuum-grown SFMO film shows the maximum value of saturation magnetization (MS) and Curie temperature (TC), signaling the lowest anti-site disorder in this series. In other words, there is a long-range Fe/Mo-O-Mo/Fe ferrimagnetic exchange in the vacuum-grown thin film, thereby enhancing the magnetization. Further, all the SFMO films show a semiconducting state with a systematic increase in overall resistivity with the increased anti-site disorder. The electrical conduction mechanism is defined by the variable-range hopping model at low temperatures. Raman spectra show a weak Fano peak, suggesting the presence of electron–phonon coupling in SFMO thin films. These results show the significance of the process gas in causing anti-site disorder, tuning the degree of this disorder and therefore its influence on the structural, magnetic, electrical, and vibrational properties of SFMO thin films. Full article
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7 pages, 1934 KiB  
Brief Report
Solution NMR Backbone Assignment of the C-Terminal Region of Human Dynein Light Intermediate Chain 2 (LIC2-C) Unveils Structural Resemblance with Its Homologue LIC1-C
Magnetochemistry 2023, 9(7), 166; https://doi.org/10.3390/magnetochemistry9070166 - 28 Jun 2023
Cited by 1 | Viewed by 676
Abstract
Dynein, a homodimeric protein complex, plays a pivotal role in retrograde transportation along microtubules within cells. It consists of various subunits, among which the light intermediate chain (LIC) performs diverse functions, including cargo adaptor binding. In contrast to the vertebrate LIC homolog LIC1, [...] Read more.
Dynein, a homodimeric protein complex, plays a pivotal role in retrograde transportation along microtubules within cells. It consists of various subunits, among which the light intermediate chain (LIC) performs diverse functions, including cargo adaptor binding. In contrast to the vertebrate LIC homolog LIC1, LIC2 has received relatively limited characterization thus far, despite partially orthogonal functional roles. In this study, we present a near-to-complete backbone NMR chemical shift assignment of the C-terminal region of the light intermediate chain 2 of human dynein 1 (LIC2-C). We perform a comparative analysis of the secondary structure propensity of LIC2-C with the one previously reported for LIC1-C and show that the two transient helices in LIC1 that interact with motor adaptors are also present in LIC2. Full article
(This article belongs to the Special Issue NMR Spectroscopy and Imaging in Biological Chemistry and Medicine)
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15 pages, 954 KiB  
Article
NMR Magnetic Shielding in Transition Metal Compounds Containing Cadmium, Platinum, and Mercury
Magnetochemistry 2023, 9(7), 165; https://doi.org/10.3390/magnetochemistry9070165 - 27 Jun 2023
Cited by 1 | Viewed by 895
Abstract
In this article, we delve into the intricate behavior of electronic mechanisms underlying NMR magnetic shieldings σ in molecules containing heavy atoms, such as cadmium, platinum, and mercury. Specifically, we explore PtXn2 (X = F, Cl, Br, I; [...] Read more.
In this article, we delve into the intricate behavior of electronic mechanisms underlying NMR magnetic shieldings σ in molecules containing heavy atoms, such as cadmium, platinum, and mercury. Specifically, we explore PtXn2 (X = F, Cl, Br, I; n = 4, 6) and XCl2Te2Y2H6 (X = Cd, Hg; Y = N, P) molecular systems. It is known that the leading electronic mechanisms responsible for the relativistic effects on σ are well characterized by the linear response with elimination of small components model (LRESC). In this study, we present the results obtained from the innovative LRESC-Loc model, which offers the same outcomes as the LRESC model but employs localized molecular orbitals (LMOs) instead of canonical MOs. These LMOs provide a chemist’s representation of atomic core, lone pairs, and bonds. The whole set of electronic mechanisms responsible of the relativistic effects can be expressed in terms of both non-ligand-dependent and ligand-dependent contributions. We elucidate the electronic origins of trends and behaviors exhibited by these diverse mechanisms in the aforementioned molecular systems. In PtX42 molecules, the predominant relativistic mechanism is the well-established one-body spin–orbit (σSO(1)) mechanism, while the paramagnetic mass–velocity (σMv) and Darwin (σDw) contributing mechanisms also demand consideration. However, in PtX62 molecules, the σ(Mv/Dw) contribution surpasses that of the SO(1) mechanism, thus influencing the overall ligand-dependent contributions. As for complexes containing Cd and Hg, the ligand-dependent contributions exhibit similar magnitudes when nitrogen is substituted with phosphorus. The only discrepancy arises from the σSO(1) contribution, which changes sign between the two molecules due to the contribution of bond orbitals between the metal and tellurium atoms. Full article
(This article belongs to the Special Issue NMR Spectroscopy in Transition Metal Complexes)
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24 pages, 11538 KiB  
Article
Interplay of Magnetic Interaction and Electronic Structure in New Structure RE-12442 Type Hybrid Fe-Based Superconductors
Magnetochemistry 2023, 9(7), 164; https://doi.org/10.3390/magnetochemistry9070164 - 26 Jun 2023
Cited by 1 | Viewed by 917
Abstract
We present detailed first-principles density functional theory-based studies on RbRE2Fe4As4O2 (RE = Sm, Tb, Dy, Ho) hybrid 12442-type iron-based superconducting compounds with particular emphasis on competing magnetic interactions and their effect on possible magneto-structural coupling and [...] Read more.
We present detailed first-principles density functional theory-based studies on RbRE2Fe4As4O2 (RE = Sm, Tb, Dy, Ho) hybrid 12442-type iron-based superconducting compounds with particular emphasis on competing magnetic interactions and their effect on possible magneto-structural coupling and electronic structure. The stripe antiferromagnetic (sAFM) pattern across the xy plane emerges as the most favorable spin configuration for all the four compounds, with close competition among the different magnetic orders along the z-axis. The structural parameters, including arsenic heights, Fe-As-Fe angle, and other relevant factors that influence superconducting Tc and properties, closely match the experimental values in stripe antiferromagnetic arrangement of Fe spins. Geometry optimization with inclusion of explicit magnetic ordering predicts a spin–lattice coupling for all the four compounds, where a weak magneto–structural transition, a tetragonal-to-orthorhombic structural transition, takes place in the relaxed stripe antiferromagnetic spin configuration. Absence of any experimental evidence of such structural transition is possibly an indication of nematic transition in RE-12442 compounds. As a result of structural distortion, the lattice contracts (expands) along the direction with parallel (anti-parallel) alignment of Fe spins. Introduction of stripe antiferromagnetic order in Fe sub-lattice reconstructs the low-energy band structure, which results in significantly reduced number of bands crossing the Fermi level. Moreover, the dispersion of bands and their orbital characteristics also are severely modified in the stripe antiferromagnetic phase similar to BaFe2As2. Calculations of exchange parameters were performed for all the four compounds. Exchange coupling along the anti-parallel alignment of Fe spins J1a is larger than that for the parallel aligned spins J1b. A crossover between the super-exchange-driven in-plane next-nearest-neighbor exchange coupling J2 and in-plane exchange coupling J1a due to lanthanide substitution was found. A large super-exchange-driven next-nearest-neighbor exchange interaction is justified using the construction of 32 maximally localized Wannier functions, where the nearest-neighbor Fe-As hopping amplitudes were found to be larger than the nearest- and the next-nearest-neighbor Fe-Fe hopping amplitudes. We compare the hopping parameters in the stripe antiferromagnetic pattern with non-magnetic configuration, and increased hopping amplitude was found along the anti-parallel spin alignment with more majority-spin electrons in Fe dxz and dxy but not in Fe dyz. On the other hand, the hopping amplitudes are increased in stripe antiferromagnetic phase along the parallel spin alignment with more majority-spin electrons in only Fe dyz. This difference in hopping amplitudes in the stripe antiferromagnetic order enables more isotropic hopping. Full article
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19 pages, 4873 KiB  
Article
Removal of Metal Ions via Adsorption Using Carbon Magnetic Nanocomposites: Optimization through Response Surface Methodology, Kinetic and Thermodynamic Studies
Magnetochemistry 2023, 9(7), 163; https://doi.org/10.3390/magnetochemistry9070163 - 24 Jun 2023
Cited by 1 | Viewed by 853
Abstract
The toxicity of metal ions on ecosystems has led to increasing amounts of research on their removal from wastewater. This paper presents the efficient application of a carbon magnetic nanocomposite as an adsorbent for the elimination of metal ions (copper, lead and zinc) [...] Read more.
The toxicity of metal ions on ecosystems has led to increasing amounts of research on their removal from wastewater. This paper presents the efficient application of a carbon magnetic nanocomposite as an adsorbent for the elimination of metal ions (copper, lead and zinc) from aqueous solutions. A Box–Behnken factorial design combined with the response surface methodology was conducted to investigate the effect and interactions of three variables on the pollutant removal process. Highly significant (p < 0.001) polynomial models were developed for each metal ion: the correlation coefficient was 0.99 for Cu(II) and Pb(II), and 0.96 for Zn(II) ion removal. The experimental data were in agreement and close to the theoretical results, which supports the applicability of the method. Working at the natural pH of the solutions, with a quantity of carbon magnetic nanocomposite of 1 g/L and a metal ions’ concentration of 10 mg/L, for 240 min, removal efficiencies greater than 75% were obtained. The kinetic study indicated that a combination of kinetic models pseudo-second order and intraparticle diffusion were applied appropriately for copper, lead and zinc ion adsorption on carbon magnetic nanocomposite. The maximum adsorption capacities determined from the Langmuir isotherm model were 81.36, 83.54 and 57.11 mg/g for copper, lead and zinc ions. The average removal efficiency for five adsorption–desorption cycles was 82.21% for Cu(II), 84.50% for Pb(II) and 72.68% for Zn(II). The high adsorption capacities of metal ions, in a short time, as well as the easy separation of the nanocomposite from the solution, support the applicability of the magnetic carbon nanocomposite for wastewater treatment. Full article
(This article belongs to the Special Issue Advances in Magnetic Behavior of Graphite and Carbon Materials)
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12 pages, 3876 KiB  
Article
Structural and Magnetic Investigations of the Novel Pyrophosphate Na7Ni3Fe(P2O7)4
Magnetochemistry 2023, 9(7), 162; https://doi.org/10.3390/magnetochemistry9070162 - 24 Jun 2023
Viewed by 930
Abstract
A novel pyrophosphate Na7Ni3Fe(P2O7)4 was synthesized in two distinct forms, single-crystal and powder. Single-crystal X-ray diffraction was used to determine the crystal structure, and powder X-ray diffraction and scanning electron microscopy were used to [...] Read more.
A novel pyrophosphate Na7Ni3Fe(P2O7)4 was synthesized in two distinct forms, single-crystal and powder. Single-crystal X-ray diffraction was used to determine the crystal structure, and powder X-ray diffraction and scanning electron microscopy were used to examine the purity and morphology of the elaborated powder. This phosphate crystallizes in the P1¯ space group of the triclinic system with a = 6.3677 (2) Å, b = 9.3316 (4) Å, c = 10.8478 (4) Å, α = 65.191 (1)°, β = 80.533 (1)° and γ = 73.042 (1)°. The crystal framework is assembled from the linkage of centro-symmetrical clusters Ni2(Ni/Fe)2P4O28. Each cluster consists of two (Fe1/Ni1)O6 octahedra, two Ni2O6 octahedra and two P2O7 units. The linkage of these clusters is provided by two other P2O7 units to generate a three-dimensional structure with distinct tunnels in the [100], [010] and [001] directions, housing the Na+ cations. The infrared and Raman analyses show the characteristic bands of the pyrophosphate anion P2O74−. Remarkably, the magnetic investigations revealed the coexistence of two magnetic transitions at ~29 K and ~4.5 K with dominating antiferromagnetic interactions. Full article
(This article belongs to the Special Issue Advances in Functional Materials with Tunable Magnetic Properties)
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17 pages, 5913 KiB  
Article
Tunable Iron–Cobalt Thin Films Grown by Electrodeposition
Magnetochemistry 2023, 9(7), 161; https://doi.org/10.3390/magnetochemistry9070161 - 21 Jun 2023
Viewed by 1079
Abstract
Iron–cobalt (FeCo) alloys are highly desirable for their exceptional and adjustable physicochemical properties, particularly in the form of thin films. This study focuses on the growth of iron–cobalt (FeCo) alloy thin films using potentiostatic electrodeposition. The effects of applied voltage and FeCo stoichiometry [...] Read more.
Iron–cobalt (FeCo) alloys are highly desirable for their exceptional and adjustable physicochemical properties, particularly in the form of thin films. This study focuses on the growth of iron–cobalt (FeCo) alloy thin films using potentiostatic electrodeposition. The effects of applied voltage and FeCo stoichiometry on the morphology, structure, and magnetic properties of the films are investigated. The results indicate that the electrodeposition potential does not affect the overall stoichiometry or the structural and magnetic properties. However, it does impact film thickness and grain sizes. Higher applied potentials lead to thicker films with faster growth rates, as well as smoother and more homogeneous films with smaller grains. Films with different Fe:Co ratios (Fe90Co10, Fe50Co50, and Fe10Co90) are obtained, and their compositions have a direct impact on morphology, with the amount of Fe influencing film thickness, growth rates, and grain sizes. Increasing Fe content (50, 90%) leads to thicker films and smaller grains. Films with low Fe content (10%) exhibit a face-centered cubic (fcc) structural phase instead of the typical body-centered cubic (bcc) structure. All FeCo alloys display soft magnetic properties with characteristic coercivities, and the low Fe (10%) sample with the fcc structure exhibits the highest coercivity among all the samples. The nucleation and growth mechanisms are investigated using electrodeposition curves and the Scharifker and Hills model. Increasing the applied potential leads to thicker films and higher growth rates, with the nucleation mechanism identified as instantaneous nucleation in the diffusion-controlled regime. Full article
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