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Magnetochemistry, Volume 8, Issue 10 (October 2022) – 26 articles

Cover Story (view full-size image): Magnetic iron oxide nanoparticles can be used to magnetically sort different types of cells in millifluidic devices. Here, the algae Nannochloropsis salina is used as an easily detectable model organism for cell sorting in flow cells. Magnetic iron oxide nanoparticles are attached to the algae cells and depending on the amount of iron oxide nanoparticles bound to the cell surface, the microorganisms are attracted by a magnet. This mechanism allows for the classification of algae cells depending on their iron oxide content. Two different geometries are investigated and compared in this study. Here, 3D printing allows for the construction of a linear flow cell geometry and for one spiraling geometry while having similar volumes for flow cell inlets and outlets. View this paper
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Article
Martensitic Transformation, Magnetic and Mechanical Characteristics in Unidirectional Ni–Mn–Sn Heusler Alloy
Magnetochemistry 2022, 8(10), 136; https://doi.org/10.3390/magnetochemistry8100136 - 21 Oct 2022
Viewed by 565
Abstract
A textured structure of Ni–Mn–Sn Heusler alloy with [001] preferred orientation has been grown by the directional solidification method. The crystal exhibits a single austenite phase L21 cubic structure (a = 5.997 Å) at room temperature. Magnetization and electronic transport [...] Read more.
A textured structure of Ni–Mn–Sn Heusler alloy with [001] preferred orientation has been grown by the directional solidification method. The crystal exhibits a single austenite phase L21 cubic structure (a = 5.997 Å) at room temperature. Magnetization and electronic transport measurements reveal the phase transformation characteristics. The maximum values of magnetic entropy change determined by Maxwell’s thermodynamic relation during the structural and magnetic phase transformations are 3.5 J/kg·K and −4.1 J/kg·K, and the total effective refrigerant capacity reaches about 314 J/kg (5 T). The evident reduction in hysteresis loss and broad operating temperature window provide a greater prospect for improving the cyclic stability of refrigeration and optimizing the application of such a magnetic refrigeration material. Both magnetoresistance (−18%, 5 T) and exchange bias field (302 Oe, 2 K) have also been investigated to understand the nature of phase transformations and exchange interactions. Furthermore, as the material exhibits excellent mechanical properties (1068 MPa, 9.0%), our experimental results provide a new reference for the application of Ni–Mn–Sn Heusler alloys. Full article
(This article belongs to the Special Issue Magnetism: Energy, Recycling, Novel Materials)
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Review
Strain-Magnetooptics in Single Crystals of CoFe2O4
Magnetochemistry 2022, 8(10), 135; https://doi.org/10.3390/magnetochemistry8100135 - 20 Oct 2022
Cited by 1 | Viewed by 488
Abstract
The strain-magnetooptical properties of single crystals of the ferrimagnetic spinel CoFe2O4, which reflect a correlation between optical properties (magnetoabsorption and magnetoreflection) and magnetostriction, have been studied in the infrared spectral range. The conditions for the observation of the strain-magnetooptics [...] Read more.
The strain-magnetooptical properties of single crystals of the ferrimagnetic spinel CoFe2O4, which reflect a correlation between optical properties (magnetoabsorption and magnetoreflection) and magnetostriction, have been studied in the infrared spectral range. The conditions for the observation of the strain-magnetooptics are specified and physical mechanisms responsible for these effects in the spinel are explained. Full article
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Article
The Effect of Obliquely Sputtered Cu Underlayers with Different Thicknesses on the Magnetic Properties of 50 nm Ni80Fe20 Thin Films
Magnetochemistry 2022, 8(10), 134; https://doi.org/10.3390/magnetochemistry8100134 - 19 Oct 2022
Viewed by 368
Abstract
The magnetic properties of 50 nm Ni80Fe20 deposited on Cu underlayers with different thicknesses by obliquely sputtering were studied. It was found that the in-plane uniaxial magnetic anisotropy (IPUMA) of the Ni80Fe20 film can be induced by [...] Read more.
The magnetic properties of 50 nm Ni80Fe20 deposited on Cu underlayers with different thicknesses by obliquely sputtering were studied. It was found that the in-plane uniaxial magnetic anisotropy (IPUMA) of the Ni80Fe20 film can be induced by the obliquely sputtered Cu underlayer deposited under the NiFe layer. The IPUMA field of NiFe film varies between 20 Oe and 40 Oe when the thickness of Cu underlayer varies from 5 nm to 50 nm. The permeability spectrum results show that the damping factor increases with increasing Cu underlayer thickness. This indicates that changing the thickness of the Cu underlayer of obliquely sputtering is an effective method to adjust the damping factor in the dynamic magnetization process of Ni80Fe20 thin films. Full article
(This article belongs to the Section Magnetic Materials)
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Article
The Synthesis of Metal–Organic-Framework-Based Ternary Nanocomposite for the Adsorption of Organic Dyes from Aqueous Solutions
Magnetochemistry 2022, 8(10), 133; https://doi.org/10.3390/magnetochemistry8100133 - 19 Oct 2022
Cited by 1 | Viewed by 472
Abstract
In the present study, a ternary magnetic nanocomposite (SiO2/MnFe2O4/ZIF-8) was synthesized via the embedding of the SiO2/MnFe2O4 nanocomposite within the metal–organic framework (ZIF-8). The synthesized nanocomposite was characterized using suitable techniques including [...] Read more.
In the present study, a ternary magnetic nanocomposite (SiO2/MnFe2O4/ZIF-8) was synthesized via the embedding of the SiO2/MnFe2O4 nanocomposite within the metal–organic framework (ZIF-8). The synthesized nanocomposite was characterized using suitable techniques including FT-IR, XRD, SEM, TEM, VSM, and BET. The nanocomposite showed a high surface area (SBET = 831 m2·g−1) and superparamagnetic behavior (23.7 emu·g−1). All characterization techniques confirmed the successful combination of three nanocomposite parts (MnFe2O4, SiO2, and ZIF-8). The nanocomposite was examined for the adsorption of organic dyes, malachite green (MG) and methyl red (MR), from aqueous solutions. The adsorption conditions including ionic strength, contact time, pH, and adsorbent dosage were optimized by studying their change effect. The SiO2/MnFe2O4/ZIF-8 nanocomposite showed high adsorption capacities (1000.03 and 1111.12 mg/g) for the removal of MG and MR, respectively, from water. The isotherm and kinetics studies indicated that the adsorption of MG and MR dyes on the surface of the SiO2/MnFe2O4/ZIF-8 nanocomposite followed the Langmuir isotherm model and pseudo-second-order kinetic model, suggesting the monolayer chemisorption mechanism. The reusability study of up to five successive cycles indicated the successful reuse of the SiO2/MnFe2O4/ZIF-8 adsorbent for dye removal from wastewater. The comparison of the present adsorbent to the previously reported adsorbents indicated that it is a promising adsorbent for dye adsorption from wastewater and must be investigated in the future for the removal of additional pollutants. Full article
(This article belongs to the Special Issue Application of Magnetic Nanomaterials in Water Pollution Treatment)
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Article
Binuclear Nickel Complexes of a New Di(hydroxyphenyl)imidazolate
Magnetochemistry 2022, 8(10), 132; https://doi.org/10.3390/magnetochemistry8100132 - 18 Oct 2022
Viewed by 464
Abstract
Here, we report a new di(hydroxyphenyl)imidazolate ligand with an N2O2 donor set synthesized by a modified Debus–Radziszewski procedure. Its binuclear nickel(II) complexes feature a weak antiferromagnetic interaction with J12 = −3.16 cm−1 between the two nickel(II) ions identified [...] Read more.
Here, we report a new di(hydroxyphenyl)imidazolate ligand with an N2O2 donor set synthesized by a modified Debus–Radziszewski procedure. Its binuclear nickel(II) complexes feature a weak antiferromagnetic interaction with J12 = −3.16 cm−1 between the two nickel(II) ions identified by magnetometry measurements. As follows from cyclic voltammetry experiments and DFT calculations, they undergo ligand-centered oxidation via the formation of cation radicals with short lifetimes that can be potentially stabilized by bulkier t-butyl groups in the ortho-positions of the ligand. The reported ligand widens the range of the building blocks available to molecular magnetism community and thus provides new ways to the design of magnetic materials with switchable properties. Full article
(This article belongs to the Special Issue Properties of Materials for Spintronic Applications)
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Review
Biological Applications of Silica-Based Nanoparticles
Magnetochemistry 2022, 8(10), 131; https://doi.org/10.3390/magnetochemistry8100131 - 18 Oct 2022
Viewed by 459
Abstract
Silica nanoparticles have been widely explored in biomedical applications, mainly related to drug delivery and cancer treatment. These nanoparticles have excellent properties, high biocompatibility, chemical and thermal stability, and ease of functionalization. Moreover, silica is used to coat magnetic nanoparticles protecting against acid [...] Read more.
Silica nanoparticles have been widely explored in biomedical applications, mainly related to drug delivery and cancer treatment. These nanoparticles have excellent properties, high biocompatibility, chemical and thermal stability, and ease of functionalization. Moreover, silica is used to coat magnetic nanoparticles protecting against acid leaching and aggregation as well as increasing cytocompatibility. This review reports the recent advances of silica-based magnetic nanoparticles focusing on drug delivery, drug target systems, and their use in magnetohyperthermia and magnetic resonance imaging. Notwithstanding, the application in other biomedical fields is also reported and discussed. Finally, this work provides an overview of the challenges and perspectives related to the use of silica-based magnetic nanoparticles in the biomedical field. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles for Biomedicine 2022)
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Article
Magnetic and Resonance Properties of a Low-Dimensional Cobalt–Aluminum Oxide–Germanium Film Tunnel Junction Deposited by Magnetron Sputtering
Magnetochemistry 2022, 8(10), 130; https://doi.org/10.3390/magnetochemistry8100130 - 18 Oct 2022
Viewed by 490
Abstract
The temperature behavior of saturation magnetization and the temperature behavior of the integral signal intensity in electron magnetic resonance spectra is experimentally studied comprehensively using a low-dimensional Al2O3/Ge/Al2O3/Co (aluminum oxide–cobalt–aluminum oxide–germanium) tunnel junction with different [...] Read more.
The temperature behavior of saturation magnetization and the temperature behavior of the integral signal intensity in electron magnetic resonance spectra is experimentally studied comprehensively using a low-dimensional Al2O3/Ge/Al2O3/Co (aluminum oxide–cobalt–aluminum oxide–germanium) tunnel junction with different deposition velocities of a ferromagnetic metal (Co) thin layer and non-magnetic layers (Al2O3/Ge/Al2O3). The cobalt ferromagnetic layer was deposited on aluminum oxide in two ways: in one cycle of creating the structure and with atmospheric injection before deposition of the cobalt layer. The thermomagnetic curves revealed the appearance of minima observed at low temperatures on both sides of the cobalt layer. Possible sources of precession perturbations at low temperatures can be explained by: the influence of the Al2O3 layer structure on the Al2O3/Co interface; residual gases in the working chamber atmosphere and finely dispersed cobalt pellets distributed over the cobalt film thickness. The work offers information of great significance in terms of practical application, for both fundamental physics and potential applications of ultrathin films. Full article
(This article belongs to the Special Issue Recent Research on Ferromagnetic Materials)
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Article
On the Distribution of Magnetic Moments in a System of Magnetic Nanoparticles
Magnetochemistry 2022, 8(10), 129; https://doi.org/10.3390/magnetochemistry8100129 - 17 Oct 2022
Viewed by 477
Abstract
Particle size distribution carries out a substantial role in the magnetic behavior of nanostructured magnetic systems. In fact, a vast literature on superparamagnetism has been reported, suggesting that the particle size distribution in a system of magnetic nanoparticles (MNPs) corresponds to a lognormal [...] Read more.
Particle size distribution carries out a substantial role in the magnetic behavior of nanostructured magnetic systems. In fact, a vast literature on superparamagnetism has been reported, suggesting that the particle size distribution in a system of magnetic nanoparticles (MNPs) corresponds to a lognormal probability density function, and several works have properly considered their magnetic moments following a similar distribution, as a universal rule. In this manuscript, it is demonstrated that alternative probability distribution functions, such as the gamma and Weibull ones, can be used to obtain useful parameters from the analysis of the magnetization curves, indicating there is no universal model to represent the actual magnetic moment distribution in a system of magnetic nanoparticles. Inspired by this observation, a reliable method to properly identify the actual magnetic moment distribution in a given nanostructured magnetic system is proposed and discussed. Full article
(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)
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Review
A Review of the Self-Powered Wiegand Sensor and Its Applications
Magnetochemistry 2022, 8(10), 128; https://doi.org/10.3390/magnetochemistry8100128 - 17 Oct 2022
Viewed by 530
Abstract
Self-powered magnetic sensors are fundamental for the development of Industry 4.0, the Internet of things (IoT), wireless sensor networks, unmanned vehicles, smart cities, and sustainability. This review aimed to elucidate the working principles, materials, manufacture, output properties, and perspectives of Wiegand sensors. A [...] Read more.
Self-powered magnetic sensors are fundamental for the development of Industry 4.0, the Internet of things (IoT), wireless sensor networks, unmanned vehicles, smart cities, and sustainability. This review aimed to elucidate the working principles, materials, manufacture, output properties, and perspectives of Wiegand sensors. A Wiegand sensor is composed of a magnetic sensing wire, which is called a Wiegand wire, and a pick-up coil for the output of an electrical signal and energy. The Wiegand sensor requires an external magnetic field of about 70 Gauss to induce Wiegand wire flux changes, which, in turn, generate an output pulse in the pick-up coil. Output energy of more than 3000 nJ per single pulse (open circuit) can be harvested. The output pulse is derived from the large Barkhausen effect. Therefore, the behavior of the sensor output is independent of the triggering and sensing frequencies. The objective of this review article was to comprehensively highlight research endeavors devoted to Wiegand sensors. Furthermore, application scenarios of current research results are highlighted to find potential gaps in the literature and future contributions. Perspectives and research opportunities of Wiegand sensors are proposed. Full article
(This article belongs to the Special Issue Spintronics, Magnetic Semiconductors and Devices)
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Article
Indocyanine Green-Containing Magnetic Liposomes for Constant Magnetic Field-Guided Targeted Delivery and Theranostics
Magnetochemistry 2022, 8(10), 127; https://doi.org/10.3390/magnetochemistry8100127 - 16 Oct 2022
Viewed by 453
Abstract
The aim of the present study was to develop magnetic liposomes (MLPSs) incorporating an agent with the ability to act both as a photosensitizer and as a fluorophore for optical imaging. We therefore aimed to develop a preparation method for indocyanine green (ICG)-containing [...] Read more.
The aim of the present study was to develop magnetic liposomes (MLPSs) incorporating an agent with the ability to act both as a photosensitizer and as a fluorophore for optical imaging. We therefore aimed to develop a preparation method for indocyanine green (ICG)-containing MLPS, followed by a detailed characterization of their physicochemical and magnetic properties. The ability of intravenously administered ICG-containing MLPSs to accumulate in tissue exposed to a constant magnetic field was tested in vivo. Using the thin film hydration method, 170-nm aqueous liposomes containing magnetic nanoparticles and indocyanine green were synthesized, followed by a detailed characterization of their physicochemical properties. It was shown that ICG-containing MLPSs possess the properties of T2 contrast for MRI. Apart from this, ICG-containing MLPSs were clearly visualized using near infrared fluorescent imaging, which was demonstrated in in vivo experiments showing an accumulation of ICG-containing MLPSs in the zone of magnetic field distribution produced by a previously implanted constant magnet in the tissue. Although not directly tested in the present study, therapeutic applications of ICG-containing MLPSs include magnetic hyperthermia, as well as the photodynamic, photothermal, and photoacoustic effects of ICG. Taking into account the fact that liposomes, iron oxide nanoparticles, and ICG are all FDA-approved agents, it is highly likely that ICG-containing MLPSs could be successfully translated to clinical practice. Full article
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Communication
Slow Magnetic Relaxation in Neutral 0D and 1D Assemblies of a Mn(III) Schiff Base Complex and Heptacyanorhenate(IV)
Magnetochemistry 2022, 8(10), 126; https://doi.org/10.3390/magnetochemistry8100126 - 14 Oct 2022
Cited by 1 | Viewed by 427
Abstract
The first neutral 0D and 1D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data of polycrystalline samples showed that both compounds display slow magnetization relaxation at temperatures below 5 K. The very low [...] Read more.
The first neutral 0D and 1D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data of polycrystalline samples showed that both compounds display slow magnetization relaxation at temperatures below 5 K. The very low temperature measurements of the magnetization on the single crystals demonstrate that for the 1D compound {[Mn(SB2+)Re(CN)7]·7H2O}n (1) and the 0D complex [Mn(SB2+)(H2O)Re(CN)7]·2H2O (2), the hysteresis loops open just below 2.2 and 1.8 K, respectively. Thus, heterometallic polymer 1 is the first single-chain magnet involving a pentagonal bipyramidal [ReIV(CN)7]3− synthon, and the binuclear complex 2 represents a single-molecule magnet. Full article
(This article belongs to the Special Issue Molecular Magnetic Materials)
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Article
Studies on the Removal of Congo Red Dye by an Adsorbent Based on [email protected]3O4 Mixture
Magnetochemistry 2022, 8(10), 125; https://doi.org/10.3390/magnetochemistry8100125 - 14 Oct 2022
Viewed by 377
Abstract
The effectiveness of a Fe3O4-loaded fly ash composite for the adsorption of Congo red dye was assessed in this work. The structure and properties of the magnetic adsorbent were established by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), [...] Read more.
The effectiveness of a Fe3O4-loaded fly ash composite for the adsorption of Congo red dye was assessed in this work. The structure and properties of the magnetic adsorbent were established by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), and dynamic light scattering (DLS). The magnetic results showed a saturation magnetization value of 6.51 emu/g and superparamagnetic behavior. The main parameters that influence the removal of Congo red dye adsorbent such as dose, initial concentration, and contact time were examined. The Freundlich adsorption isotherm and pseudo-second-order kinetic model provided the best fit for the experimental findings. The Congo red dye’s maximum adsorption capacity of 154 mg/g was reported in the concentration range of 10–100 mg/L, using the proposed magnetic adsorbent. The results of the recyclability investigation demonstrated that the circular economy idea is valid. The adsorbent that was synthesized was also further characterized by XRD and FTIR techniques after Congo red dye adsorption. Full article
(This article belongs to the Special Issue Advances in Magnetic Microspheres)
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Article
Structural, Microstructural and Magnetic Properties of SmCo5/20wt%Fe Magnetic Nanocomposites Produced by Mechanical Milling in the Presence of CaO
Magnetochemistry 2022, 8(10), 124; https://doi.org/10.3390/magnetochemistry8100124 - 11 Oct 2022
Viewed by 331
Abstract
In this work, we demonstrate the possibility of using a soluble ceramic material, 5 wt% CaO, as an additive for an SmCo5/20wt%Fe exchange-coupled nanocomposite obtained by mechanical milling in order to inhibit the grain growth of the soft magnetic phase during [...] Read more.
In this work, we demonstrate the possibility of using a soluble ceramic material, 5 wt% CaO, as an additive for an SmCo5/20wt%Fe exchange-coupled nanocomposite obtained by mechanical milling in order to inhibit the grain growth of the soft magnetic phase during annealing, which results in a more stable microstructure and an implicit improvement in the hard–soft interphase exchange coupling. Moreover, we show that the additive improves the phase stability of the composite material, reducing the amount of Sm2Co17-type phases formed during the synthesis process, an important aspect because Sm2Co17 is detrimental to the magnetic performance of the SmCo5/20%Fe nanocomposite. These effects are reflected in a nearly 13% increase in the coercive field (Hc) and a 20% increase in the energy product, (BH)max, for the powders produced using CaO as compared to pure SmCo5/20%Fe nanocomposites processed in the same manner. Full article
(This article belongs to the Special Issue Advanced Nanomagnetic Material)
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Opinion
Translational Hurdles with Magnetic Nanoparticles and Current Clinical Scenario in Hyperthermia Applications
Magnetochemistry 2022, 8(10), 123; https://doi.org/10.3390/magnetochemistry8100123 - 09 Oct 2022
Viewed by 455
Abstract
Magnetic Nanoparticles (MNPs) are becoming increasingly popular for biomedical imaging and drug delivery, particularly cancer theranostics. Due to their excellent inherent properties and the accessibility to be tailor-made according to specific requirements, they stand out from the crowd and are close, yet so [...] Read more.
Magnetic Nanoparticles (MNPs) are becoming increasingly popular for biomedical imaging and drug delivery, particularly cancer theranostics. Due to their excellent inherent properties and the accessibility to be tailor-made according to specific requirements, they stand out from the crowd and are close, yet so far. While the number of publications related to MNPs’ drug-delivery systems reported in the literature increases yearly, relatively more minor conversion has been observed from the bench to the bedside. It is of paramount importance to understand and work on the shortcomings and redesign the strategies to increase the clinical translatability of MNPs. ‘Supply as per Demand’ should be followed while designing an MNP-based delivery system. To achieve this, a better understanding of the clinical issues should be addressed early, and downstream methods should be prepared to resolve them. More significantly, all clinical problems in one delivery system should be eliminated, and one problem and one solution should be pursued. This opinion review explores the current limitations in evaluating magnetic nanoparticle performance, suggesting a promising standardized pathway to clinical translation. Full article
(This article belongs to the Special Issue Biomedical Application of Magnetic Nanoparticles in 2022)
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Article
Magnetic, Electric and Optical Properties of Ion Doped CuCr2O4 Nanoparticles
Magnetochemistry 2022, 8(10), 122; https://doi.org/10.3390/magnetochemistry8100122 - 07 Oct 2022
Viewed by 404
Abstract
The magnetic, electric and optical properties of pure and ion doped CuCr2O4 - bulk and nanoparticles are investigated theoretically. The magnetization Ms and the band gap Eg decrease with increasing particle size. By Co ion doping Ms [...] Read more.
The magnetic, electric and optical properties of pure and ion doped CuCr2O4 - bulk and nanoparticles are investigated theoretically. The magnetization Ms and the band gap Eg decrease with increasing particle size. By Co ion doping Ms and the polarization P show a maximum whereas by Pr ion doping they decrease with increasing the doping concentration. The dielectric constant decreases with enhancing Pr dopants. It is shown that the difference between the doping and host ions radii leads to appearing of a compressive or tensile strain and to different exchange interaction constants in the doped state. Eg decreases by Co doping, whereas it increases by Pr doping. Full article
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Article
Exploring the Polarization of Light in Ferrofluids with Mueller Matrices
Magnetochemistry 2022, 8(10), 121; https://doi.org/10.3390/magnetochemistry8100121 - 07 Oct 2022
Viewed by 627
Abstract
We studied the polarization of light in a thin film of ferrofluid subjected to a magnetic field using the Mueller matrix formalism. By observing the results of some experiments, we relate the observed light patterns with Stokes vectors that can be operated by [...] Read more.
We studied the polarization of light in a thin film of ferrofluid subjected to a magnetic field using the Mueller matrix formalism. By observing the results of some experiments, we relate the observed light patterns with Stokes vectors that can be operated by Mueller matrices, which represent the magnetic field applied to the sample. We observed that the changes in the dichroism of this system can be monitored along the sample, allowing for the visualization of magneto-optical effects mainly for linear polarized light, and the effects of circular polarized light are related to birefringence. Full article
(This article belongs to the Special Issue Ferrofluids - Electromagnetic Properties and Applications)
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Article
Structural and Photocatalytic Studies on Oxygen Hyperstoichiometric Titanium-Substituted Strontium Ferrite Nanoparticles
Magnetochemistry 2022, 8(10), 120; https://doi.org/10.3390/magnetochemistry8100120 - 06 Oct 2022
Viewed by 510
Abstract
Doping of ferrites is an important domain of research for their application as photocatalysts. In the present work, the effect of Ti4+ substitution on the structural and photocatalytic properties of strontium ferrite nanoparticles (NPs) is studied. Ternary doped Sr1−xTix [...] Read more.
Doping of ferrites is an important domain of research for their application as photocatalysts. In the present work, the effect of Ti4+ substitution on the structural and photocatalytic properties of strontium ferrite nanoparticles (NPs) is studied. Ternary doped Sr1−xTixFe2O4+δ ferrite NPs (x = 0.0–1.0) were synthesized by sol–gel methodology. Tetravalent Ti4+ ions caused oxygen hyperstoichiometry and enhancement in the surface area from 44.3 m2/g for SrFe2O4 NPs to 77.6 m2/g for Sr0.4Ti0.6Fe2O4+δ NPs. The average diameter of NPs ranged between 25–35 nm as revealed by TEM analysis. The presence of two sextets in the Mössbauer spectrum of pristine SrFe2O4 and Ti4+-substituted ferrite NPs and a paramagnetic doublet in the TiFe2O5 confirmed their phase purity. The photocatalytic potential of pure and Ti4+-substituted ferrite NPs was studied using nitroaromatic compounds, viz. pendimethalin, p-nitrophenol and Martius yellow, as model pollutants. Doped ferrite NPs with a composition of Sr0.4Ti0.6Fe2O4+δ NPs showed the highest degradation efficiency ranging from 87.2% to 94.4%. The increased photocatalytic potential was ascribed to the lowering of band gap (Eg) from 2.45 eV to 2.18 eV, a fourfold decrease in photoluminescence intensity, increased charge carrier concentration (4.90 × 1015 cm−3 to 6.96 × 1015 cm−3), and decreased barrier height from 1.20 to 1.02 eV. O2●− radicals appeared to be the main reactive oxygen species involved in photodegradation. The apparent rate constant values using the Langmuir–Hinshelwood kinetic model were 1.9 × 10−2 min−1, 2.3 × 10−2 min−1 and 1.3 × 10−2 min−1 for p-nitrophenol, pendimethalin and Martius yellow, respectively. Thus, tuning the Ti4+ content in strontium ferrite NPs proved to be an effective strategy in improving their photocatalytic potential for the degradation of nitroaromatic pollutants. Full article
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Article
Dynamic Bloch Chirality and Enhanced Velocities from Spin-Orbit Torque Driven Domain Wall Motion in Thick Magnetic Films
Magnetochemistry 2022, 8(10), 119; https://doi.org/10.3390/magnetochemistry8100119 - 06 Oct 2022
Viewed by 507
Abstract
Spin-orbit torque (SOT) driven domain wall motion has attracted significant attention as the basis for a variety of spintronic devices due to its potential use as a high speed, low power means to manipulate the magnetic state of an object. While most previous [...] Read more.
Spin-orbit torque (SOT) driven domain wall motion has attracted significant attention as the basis for a variety of spintronic devices due to its potential use as a high speed, low power means to manipulate the magnetic state of an object. While most previous attention has focused on ultrathin films wherein the material thickness is significantly less than the magnetic exchange length, recent reports have suggested unique dynamics may be achieved in intermediate and high thickness films. We used micromagnetic modelling to explore the role of the vertically non-uniform spin textures associated with the domain wall in nanowires of varying thickness on SOT driven domain wall motion. We found large velocity asymmetries between Bloch chiralities near the current density required for reversal of the Bloch component of the magnetization and linked these asymmetries to a gradual reorientation of the domain wall structure which drives a non-negligible, chiral Néel component of the domain wall. We further explored the influence of saturation magnetization, film thickness, the Dzyaloshinskii-Moriya interaction, and in-plane fields on domain wall dynamics. These results provide a framework for the development of SOT based devices based on domain wall motion in nanowires beyond the ultrathin film limit. Full article
(This article belongs to the Special Issue Magnetic and Transport Properties of Thin-Film Materials)
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Article
Two-Step Calcination-Method-Derived Al-Substituted W-Type SrYb Hexaferrites: Their Microstructural, Spectral, and Magnetic Properties
Magnetochemistry 2022, 8(10), 118; https://doi.org/10.3390/magnetochemistry8100118 - 30 Sep 2022
Viewed by 473
Abstract
W-type hexaferrites were discovered in the 1950s and are of interest for their potential applications. In this context, many researchers have conducted studies on the partial substitution of Fe sites in order to modify their electric and magnetic properties. In this study, W-type [...] Read more.
W-type hexaferrites were discovered in the 1950s and are of interest for their potential applications. In this context, many researchers have conducted studies on the partial substitution of Fe sites in order to modify their electric and magnetic properties. In this study, W-type SrYb hexaferrites using Al3+ as substitutes for Fe3+ sites with the nominal composition Sr0.85Yb0.15Zn1.5Co0.5AlxFe16−xO27 (0.00 ≤ x ≤ 1.25) were successfully synthesized via the two-step calcination method. The microstructures, spectral bands of characteristic functional groups, morphologies, and magnetic parameters of the prepared samples were characterized using XRD, FTIR, SEM, EDX, and VSM. The XRD results showed that, compared with the standard patterns for the W-type hexaferrite, the W-type SrYb hexaferrites with the Al content (x) of 0.00 ≤ x ≤ 1.25 were a single-W-type hexaferrite phase. SEM images showed the flakes and hexagonal grains of W-type hexaferrites with various Al content (x). The saturation magnetization (Ms) and magneton number (nB) decreased with Al content (x) from 0.00 to 1.25. The remanent magnetization (Mr) and coercivity (Hc) decreased with Al content (x) from 0.00 to 0.25. Additionally, when the Al content (x) ≥ 0.25, Mr and Hc increased with the increase in the Al content (x). The magnetic anisotropy field (Ha) and first anisotropy constant (K1) increased with the Al content (x) increasing from 0.00 to 1.25. Al-substituted W-type SrYb hexaferrites with soft magnetic behavior, high Ms, and lower Hc may be used as microwave-absorbing materials. Full article
(This article belongs to the Special Issue Hexagonal Ferrites: Synthesis, Structure and Properties)
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Article
Synergistic Effect of Combined Treatment with Magnetic Hyperthermia and Magneto-Mechanical Stress of Breast Cancer Cells
Magnetochemistry 2022, 8(10), 117; https://doi.org/10.3390/magnetochemistry8100117 - 29 Sep 2022
Viewed by 629
Abstract
With the development of nanotechnology, the emergence of new anti-tumor techniques using nanoparticles such as magnetic hyperthermia and magneto-mechanical activation have been the subject of much attention and study in recent years, as anticancer tools. Therefore, the purpose of the current in vitro [...] Read more.
With the development of nanotechnology, the emergence of new anti-tumor techniques using nanoparticles such as magnetic hyperthermia and magneto-mechanical activation have been the subject of much attention and study in recent years, as anticancer tools. Therefore, the purpose of the current in vitro study was to investigate the cumulative effect of a combination of these two techniques, using magnetic nanoparticles against breast cancer cells. After 24 h of incubation, human breast cancer (MCF-7) and non-cancerous (MCF-10A) cells with and without MNPs were treated (a) for 15 min with magnetic hyperthermia, (b) for 30 min with magneto-mechanical activation, and (c) by a successive treatment consisting of a 15-min magnetic hyperthermia cycle and 30 min of magneto-mechanical activation. The influence of treatments on cell survival and morphology was studied by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assay and light microscopy. When applied, separately, magneto-mechanical and thermal (hyperthermia) treatment did not demonstrate strong reduction in cell viability. No morphological changes were observed in non-cancerous cells after treatments. On the other hand, the combination of magneto-mechanical and thermal treatment in the presence of MNPs had a synergistic effect on decreased cell viability, and apoptosis was demonstrated in the cancer cell line. Synergism is most evident in the cancer cell line, incubated for 120 h, while in the non-cancerous line after 120 h, an increase in proliferation is clearly observed. MCF-7 cells showed more rounded cell morphology, especially after 120 h of combined treatment. Full article
(This article belongs to the Special Issue Biomedical Application of Magnetic Nanoparticles in 2022)
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Article
Solid-State Self-Assembly of a Linear Hexanuclear Copper(II) Oxamate Complex with Alternating Antiferro- and Ferromagnetic Coupling
Magnetochemistry 2022, 8(10), 116; https://doi.org/10.3390/magnetochemistry8100116 - 28 Sep 2022
Viewed by 611
Abstract
In this work, we describe the synthesis, crystal structure and magnetic properties of the neutral hexacopper(II) complex of formula {[Cubpca)]2[Cu(dmopba)(H2O)]}2·4H2O (1), where Hbpca = bis(2-pyridylcarbonyl)-amide and dmopba = 4,5-dimethyl-1,2-phenylenebis(oxamato). Single crystals of 1 [...] Read more.
In this work, we describe the synthesis, crystal structure and magnetic properties of the neutral hexacopper(II) complex of formula {[Cubpca)]2[Cu(dmopba)(H2O)]}2·4H2O (1), where Hbpca = bis(2-pyridylcarbonyl)-amide and dmopba = 4,5-dimethyl-1,2-phenylenebis(oxamato). Single crystals of 1 were obtained from the stoichiometric reaction (1:2 molar ratio) of the mononuclear copper(II) complexes (n-Bu4N)2[Cu(dmpba)] and [Cu(bpca)(H2O)2]NO3·2H2O through slow diffusion techniques in water as a solvent. The crystal structure of 1 shows that two neutral {[Cu(bpca)]2[Cu(dmopba)(H2O)]} trinuclear units are connected through double out-of-plane copper to outer carboxylate oxygen atoms resulting in a unique oxamate-bridged linear hexanuclear complex. Hydrogen bonds among adjacent entities involving the non-coordinated water molecules result in a supramolecular 3D network. Magnetic measurements on 1 show the occurrence of moderate antiferromagnetic intratrinuclear interactions between the copper(II) ions from the [Cu(bpca)]+ and [Cu(dmopba)(H2O)]2− fragments across the oxamate bridge and a weak intertrinuclear ferromagnetic interaction between the copper(II) ions that occurs between the two central [Cu(bpca)]+ fragments mediated by the carboxylate groups from the oxamate bridge [J = −31.96(2) cm−1 and J′ = +1.34(2) cm−1; H = J (S1·S2 + S2·S3 + S1′·S2′ + S2′·S3′) + J′ (S1·S1′)]. Full article
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Article
Cosmological Phase Transitions—EWPT-QCDPT: Magnetic Field Creation
Magnetochemistry 2022, 8(10), 115; https://doi.org/10.3390/magnetochemistry8100115 - 27 Sep 2022
Viewed by 495
Abstract
We review the cosmic microwave background (CMBR) estimate of ordinary matter, dark matter and dark energy in the universe. Then, we review the cosmological electroweak (EWPT) and quantum chromodynamics (QCDPT) phase transitions. During both the EWPT and QCDPT, bubbles form and collide, producing [...] Read more.
We review the cosmic microwave background (CMBR) estimate of ordinary matter, dark matter and dark energy in the universe. Then, we review the cosmological electroweak (EWPT) and quantum chromodynamics (QCDPT) phase transitions. During both the EWPT and QCDPT, bubbles form and collide, producing magnetic fields. We review dark matter produced during the EWPT and the estimate of dark matter via galaxy rotation. Full article
(This article belongs to the Special Issue Magnetodynamics of Space Plasmas)
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Article
Doxorubicin-Loaded Magnetic Nanoparticles: Enhancement of Doxorubicin’s Effect on Breast Cancer Cells (MCF-7)
Magnetochemistry 2022, 8(10), 114; https://doi.org/10.3390/magnetochemistry8100114 - 23 Sep 2022
Viewed by 624
Abstract
The incidence of female breast cancer has increased; it is the most commonly diagnosed cancer, at 11.7% of the total, and has the fourth highest cancer-related mortality. Magnetic nanoparticles have been used as carriers to improve selectivity and to decrease the side effects [...] Read more.
The incidence of female breast cancer has increased; it is the most commonly diagnosed cancer, at 11.7% of the total, and has the fourth highest cancer-related mortality. Magnetic nanoparticles have been used as carriers to improve selectivity and to decrease the side effects on healthy tissues in cancer treatment. Iron oxide (mainly magnetite, Fe3O4), which presents a low toxicity profile and superparamagnetic behavior, has attractive characteristics for this type of application in biological systems. In this article, synthesis and characterization of magnetite (NP-Fe3O4) and silica-coated magnetite (NP-Fe3O4/SiO2) nanoparticles, as well as their biocompatibility via cellular toxicity tests in terms of cell viability, are carefully investigated. MCF-7 cells, which are commonly applied as a model in cancer research, are used in order to define prognosis and treatment specifics at a molecular level. In addition, HaCaT cells (immortalized human keratinocytes) are tested, as they are normal, healthy cells that have been used extensively to study biocompatibility. The results provide insight into the applicability of these magnetic nanoparticles as a drug carrier system. The cytotoxicity of nanoparticles in breast adenocarcinoma (MCF-7) and HaCat cells was evaluated, and both nanoparticles, NP-Fe3O4/SiO2 and NP-Fe3O4, show high cell viability (non-cytotoxicity). After loading the anti-tumor drug doxorubicin (Dox) on NP-Fe3O4/Dox and NP-Fe3O4/SiO2/Dox, the cytotoxicity against MCF-7 cells increases in a dose-dependent and time-dependent manner at concentrations of 5 and 10 μg/mL. HaCat cells also show a decrease in cell viability; however, cytotoxicity was less than that found in the cancer cell line. This study shows the biocompatibility of NP-Fe3O4/SiO2 and NP-Fe3O4, highlighting the importance of silica coating on magnetic nanoparticles and reinforcing the possibility of their use as a drug carrier system against breast adenocarcinoma cells (MCF-7). Full article
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Article
Magnetophoretic Cell Sorting: Comparison of Different 3D-Printed Millifluidic Devices
Magnetochemistry 2022, 8(10), 113; https://doi.org/10.3390/magnetochemistry8100113 - 21 Sep 2022
Viewed by 559
Abstract
Cell sorting is a highly applicable technology for multiple biological, biotechnological, and medical applications. Magnetic cell sorting can be realized with microfluidic and millifluidic flow cells. Additive manufacturing and 3D printing allow for fast prototyping and validating separation processes on this small scale. [...] Read more.
Cell sorting is a highly applicable technology for multiple biological, biotechnological, and medical applications. Magnetic cell sorting can be realized with microfluidic and millifluidic flow cells. Additive manufacturing and 3D printing allow for fast prototyping and validating separation processes on this small scale. Therefore, our novel approach is to use this technology to print millifluidic channels and to directly evaluate them on their magnetic separation performance and their handling for cell manipulation. In this study, two different flow cells manufactured with a 3D printer are compared in regard to their use for the magnetic cell sorting of algae. One linear flow cell geometry and one spiraling flow cell geometry have been investigated with perpendicular magnetic fields. Iron oxide nanoparticles have been synthesized and characterized prior to their use as a magnetic label for algae cells. Particle uptake by algae are investigated by a phenanthroline assay, and the particle/algae mixtures are studied by microscopy, dynamic light scattering, zeta potential, and magnetophoretic mobility measurements. Depending on magnetic susceptibility, the cells undergo different magnetophoretic forces. Interestingly, the spiraling geometry leads to a better fractionation of algae cells in accordance with their iron oxide load. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles for Biomedicine 2022)
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Article
Magnetic Properties of a Solid Solution Fe1−xAgxCr2S4 (0 < x < 0.2)
Magnetochemistry 2022, 8(10), 112; https://doi.org/10.3390/magnetochemistry8100112 - 21 Sep 2022
Viewed by 606
Abstract
The magnetic properties of the Fe1−xAgxCr2S4 (0 < x < 0.2) solid solution were investigated in the temperature range 4–300 K in a DC field of 0.1 and 45 kOe. Fe1−xAgxCr2 [...] Read more.
The magnetic properties of the Fe1−xAgxCr2S4 (0 < x < 0.2) solid solution were investigated in the temperature range 4–300 K in a DC field of 0.1 and 45 kOe. Fe1−xAgxCr2S4 is characterized by the transition temperature from the paramagnetic to the ferromagnetic state (Tc) and the irreversibility temperature (Tirr). The replacement of iron with silver ions in Fe1−xAgxCr2S4 leads to an increase in the Curie temperatures from 185 K (x = 0) to 216 K (x = 0.2) and Tcusp from 45 K (x = 0) to 125 K (x = 0.2). A section of the Fe1−xAgxCr2S4 magnetic phase diagram in the region under study has been constructed. The diagram reveals the following regions: paramagnetic, ferromagnetic, region of conditionally recurrent spin-glass (SG), and below 10 K a region associated with orbital ordering. Full article
(This article belongs to the Special Issue Ferrimagnetic Materials: State of the Art and Future Perspectives)
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Article
Magnetic Properties Regulation of FeGa and FeGaNi Films with Oblique Magnetron Sputtering
Magnetochemistry 2022, 8(10), 111; https://doi.org/10.3390/magnetochemistry8100111 - 20 Sep 2022
Viewed by 513
Abstract
Magnetic FeGa and FeGaNi films with an in-plane anisotropy were deposited by employing oblique magnetron sputtering. With the increase in oblique angle, the crystallite size of FeGa decreases, which indicates that oblique sputtering can refine the crystallite size. The remanence ratio of FeGa [...] Read more.
Magnetic FeGa and FeGaNi films with an in-plane anisotropy were deposited by employing oblique magnetron sputtering. With the increase in oblique angle, the crystallite size of FeGa decreases, which indicates that oblique sputtering can refine the crystallite size. The remanence ratio of FeGa films increases from 0.5 to 0.92 for an easy axis, and the coercivity increases with the decrease in the crystallite size. The calculated static anisotropic field shows that the in-plane magnetic anisotropy can be induced by oblique sputtering and the strength increases with the oblique sputtering angle. After doping Ni by co-sputtering, FeGaNi films exhibit a stable remanence ratio at 0.8, low coercivity and good anisotropy. With the low sputtering power of the Ni target, there is a competitive relationship between the effect of crystallite size and Ni doping which causes the coercivity of FeGaNi films to first increase and then decrease with the increase in the oblique angle. The FeGaNi film also shows high anisotropy in a small oblique angle. The variation of coercivity and anisotropy of FeGaNi films can be explained by the crystalline size effect and increase in Ni content. For the increasing intensity of collisions between FeGa and Ni atoms in the co-sputtering, the in-plane magnetic anisotropy increases first and then decreases. As a result, the magnetic properties of FeGa films were examined to tailor their magnetic softness and magnetic anisotropy by controlling the oblique sputtering angle and Ni doping. Full article
(This article belongs to the Special Issue Recent Research on Ferromagnetic Materials)
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