Magnetochemistry

In this study, we investigated the temperature dependencies of the total, crystal lattice, and electronic thermal conductivities in films of topological insulators p–Bi_0.5Sb_1.5Te₃ and p–Bi₂Te₃ formed by discrete and thermal evaporation methods. The largest decrease in the lattice thermal conductivity because of the scattering of long-wavelength phonons on the grain interfaces was observed in the films of the solid-solution p–Bi_0.5Sb_1.5Te₃ deposited by discrete evaporation on the amorphous substrates of polyimide without thermal treatment. It was shown that in the p–Bi_0.5Sb_1.5Te₃ films with low thermal conductivity, the energy dependence of the relaxation time is enhanced, which is specific to the topological insulators. The electronic thermal conductivity was determined by taking into account the effective scattering parameter in the relaxation time approximation versus energy in the Lorentz number calculations. A correlation was established between the thermal conductivity and the peculiarities of the morphology of the interlayer surface (0001) in the studied films. Additionally, the total κ and the lattice κ_L thermal conductivities decrease, while the number of grains and the roughness of the surface (0001) increase in unannealed films compared to annealed ones. It was demonstrated that increasing the thermoelectric figure of merit ZT in the p–Bi_0.5Sb_1.5Te₃ films formed by discrete evaporation on a polyimide substrate is determined by an increase in the effective scattering parameter in topological insulators due to enhancement in the energy dependence of the relaxation time. Full article

Nanocrystalline La_0.9A_0.1Mn_0.9Cr_0.1O₃ (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology were studied using X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning electron microscopy (SEM). Magnetic properties were studied using magnetometry methods and the valency changes of the cations after alkali ions doping were studied using X-ray photoelectron spectroscopy (XPS). The influence of the sintering pressure on the structural and magnetic properties of the manganites doped with different alkali ions and chromium was also investigated. Magnetization properties were studied as a function of sintering pressure and type of the dopant. Chemical doping with alkali ions as well as external pressure significantly changed the magnetic properties of the compounds. It was found that the magnetic properties of the manganites could be predictably modified through the use of a suitable dopant element. Full article

The aim of this study was to investigate the magnetic properties of mixed nanocrystalline Zn/manganese oxide compounds synthesized by a hydrothermal method. These compounds are designed as (ZnO)_1−n(MnO)_n, where index n ranges from 0.05 to 0.60. The results of magnetic measurements, including AC magnetic susceptibility as a function of temperature (up to 160 K) and frequency (from 7 Hz up to 9970 Hz), as well as DC magnetization in magnetic fields up to 9 T and temperature up to 50 K, are reported. We observed various types of magnetic behavior depending on the nominal weight content of MnO. Samples with a low nominal content (up to n = 0.10) of MnO exhibited Curie–Weiss behavior at higher temperatures. For samples with high nominal weight contribution (from n = 0.30 to 0.60), spin-glass-like or/and weak ferromagnetic behavior is observed. Full article

We report on the results of first principles calculations investigating the influences of Mn doping on the local moments and stacking fault energies (SFEs) in the Co${}_{95.8}$Mn${}_{4.2}$ and Co${}_{91.6}$Mn${}_{8.4}$ systems as compared to pure face-centered cubic Co. A supercell was developed to maintain periodicity in calculations, provide a simple relaxation mechanism, and allow for easy expansion to accommodate different concentrations of Mn. Calculations to determine the generalized SFE were performed on relaxed and non-relaxed systems in both ferromagnetic and nonmagnetic states. Analysis revealed fluctuations in the magnetic moments that are closely tied to the relaxation state and faulting state of the system. In the case of systems containing Mn, we observed a dependence of the SFE on the location of the Mn atom(s) within the supercell relative to the stacking fault interface and a strong induced magnetic moment for these atoms. Full article

This work is devoted to the study of exchange interactions between rare earth atoms in the LaAlO₃ matrix. Using the magnetic dilution method, the study of concentration and temperature dependences of magnetic susceptibility and effective magnetic moments of diluted solid solutions the magnetic characteristics of single rare earth atoms and the character of superexchange between them are described—antiferromagnetic at low concentrations, and for samarium, predominantly ferromagnetic within greater clusters as the concentration increases. The development of superexchange is similar to the exchange between d-elements in the same matrix. Full article

Magnetic nanoparticles are a promising alternative as a support in adsorption processes, aiming at the easy recovery of the aqueous medium. A faujasite zeolite (FAU) surface was decorated with magnesium ferrite (MgFe₂O₄) nanoparticles. FAU is a porous adsorbent with high specific surface area (SSA) and chemical stability. The FAU:MgFe₂O₄ nanocomposite 3:1 ratio (w w⁻¹) promotes the combination of the surface and magnetic properties. The results showed the effectiveness of the MgFe₂O₄ immobilization on the FAU surface, exhibiting a high SSA of 400 m² g⁻¹. The saturation magnetization (Ms) was verified as 5.9 emu g⁻¹ for MgFe₂O₄ and 0.47 emu g⁻¹ for FAU:MgFe₂O₄, an environmentally friendly system with soft magnetic characteristics. The magnetic nanocomposite achieved high adsorption values of around 94% removal for Co²⁺ and Mn²⁺ ions. Regarding its reuse, the nanocomposite preserved adsorption activity of above 65% until the third cycle. Thus, the FAU:MgFe₂O₄ nanocomposite presented favorable adsorptive, magnetic, and recovery properties for reuse cycles in polluted water. Full article

We investigate the gap symmetry of the topological superconductor candidate HfRuP, which crystallizes in a noncentrosymmetric hexagonal crystal structure, using muon spin rotation/relaxation ($\mu$SR) measurements in transverse-field (TF) geometry. The temperature and magnetic field dependencies of the superconducting relaxation rate derived from the TF-$\mu$SR spectra can be well described by an isotropic s-wave gap. The superconducting carrier density $n_s$ = 1.41(1) × 10${}^{26}$ m${}^{-3}$ and the magnetic penetration depth, $\lambda$(0) = 603(2) nm, were calculated from the TF-$\mu$SR data. Interestingly, the ratio between the superconducting transition temperature and the superfluid density, $T_c$/$\lambda$${}^{-2}$(0) ∼ 3.3, is very close to those of unconventional superconductors. Further, our zero-field (ZF) $\mu$SR results do not show any considerable change in the muon spin relaxation above and below the superconducting transition temperature, suggesting that time-reversal symmetry is preserved in the superconducting state of this superconductor. Full article

Magnetic fluid seals have long been thought to be a successful sealing form while sealing liquids are always a challenge. The instability of the liquid–liquid interface under the washout has become the key technical problem that hinders the realization of sealing liquid. This work mainly presents an experimental study about the influence of high viscosity and magnetoviscous effects on washout resistance. Three engine oil-based magnetic fluids of different viscosities were prepared with two kinds of surfactants. The magnetoviscous effects of the prepared magnetic fluids under different working conditions were found through rheological experiments. The viscosity of the three samples decreased at most by about 100 times with the shear rate increasing. An experimental platform was designed and built for the washout tests. The entire process of magnetic fluids being washed away was obtained experimentally. The magnetic fluid of higher viscosity can remain stationary with lower magnetic force. The quantitative results show that the viscosity of the magnetic fluid has a significant influence on washout resistance under a magnetic field. Full article

In this first volume, we cover relevant aspects of chemical and physical processes of the production and characterization of magnetic materials in bulk, thin films, nanostructures, and/or nanocomposites, as well as modeling aspects involving such structures. Accordingly, this volume presents eleven original research and review works on the challenges and trends covering fundamental and experimental work, with a special focus on the design, synthesis, and characterization of various types of magnetic materials, and the study of their structure–property relationships. State-of-the-art results on the development of new experimental concepts, leading to the transfer, chemical transformation, and high-resolution patterning of advanced thin films and nanomaterials, and to the design and fabrication of devices, are also presented and discussed. Full article

Herein, we report a procedure for separating and preconcentrating antibiotics from human serum using a novel adsorbent of magnetic graphene oxide (MGO) and cadmium sulfide (CdS) nanoparticles. The adsorbent ([email protected]) was characterized using Fourier transformed infrared spectrometry (FT-IR), energy dispersive X-ray spectroscopy (EDX), and field emission scanning electron microscopy (FE-SEM). The effective parameters for extraction efficiency were investigated, including the desorption solvent’s nature, pH, adsorbent dose, salt concentration, extraction time, and volume of sample solution and desorption solvent. The proposed procedure proved to be fast (20 min), simple (two stages), and cost-effective (20 mg of nanoparticles). Under the optimum conditions, satisfactory linearity (R2 > 0.992) was obtained, and limits of detection (LOD) were estimated as 4.5 µg L⁻¹ (for tetracycline) and 5.7 µg L⁻¹ (for penicillin) and a linear dynamic range (LDR) from 20 to 200 µg L⁻¹. The magnetic solid phase extraction (MSPE) method based on [email protected] has achieved a satisfactory recovery (71.5–109.5%) in human serum for the selected antibiotics. Finally, the antibiotic’s release was studied in simulated fluids of the gastric (pH = 1.2) and intestine (pH = 7.4). In this light, we demonstrate that the newly introduced adsorbent can be used in drug extraction from different biological media. Full article

The reaction of [Ln(btfa)₃(H₂O)₂] (btfa⁻ = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate) with additional 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbtfa) and acridine (Acr) in ethanol allows the isolation of the mononuclear compounds HAcr[Nd(btfa)₄]·EtOH, (1) and HAcr[Ln(btfa)₄], Ln = Dy (2) and Yb (3); HAcr⁺ = acridinium cation. Magnetic measurements indicate that complexes 1–3 show field-induced single-ion magnet behavior with anisotropy energy barriers and preexponential factors of U_eff = 20.7 cm⁻¹, τ₀ = 24.5 × 10⁻⁸ s; U_eff = 40.5 cm⁻¹, τ₀ = 8.6 × 10⁻¹⁰ s and U_eff = 22.7 cm⁻¹, τ₀ = 8.4 × 10⁻⁸ s, for 1–3 respectively. The solid-state luminescence emission in the NIR region shows efficient energy transfer from the 4,4,4-trifluoro-1-phenyl-1,3-butanedionate ligands to the central Ln³⁺ ion in the case of compounds 1 and 3. Full article

A new mixed-valence one-dimensional coordination polymer of formula {[Co^II(MeOH)₂][(μ-NC)₂Co^III(dmphen)(CN)₂]₂}_n·2nH₂O (1) was obtained by reacting the Ph₄P[Co^II(dmphen)(CN)₃] metalloligand (dmphen = 2,9-dimethyl-1,10-phenanthroline and Ph₄P⁺ = tetraphenylphosphonium ion) with cobalt(II) acetate tetrahydrate. The structural analysis shows the formation of a neutral 4,2-ribbon-like chain of vertex-sharing cyanido-bridged {Co^III₂Co^II₂} squares in which the metalloligand underwent an oxidation process and a reorganization to form {Co^III(dmphen)(CN)₄}⁻ linkers that coordinate to the [Co^II(MeOH)₂]²⁺ units through single cyanido ligands. Both cobalt(II) and Co(III) cations are six-coordinated in distorted octahedral environments. The shortest intrachain distance between the paramagnetic cobalt(II) ions is 7.36 Å, a value which is shorter than the shortest interchain one (10.36 Å). Variable-temperature (1.9–300 K) static (dc) magnetic measurements for 1 indicate the occurrence of magnetically isolated high-spin cobalt(II) ions with a D value of +67.0 cm⁻¹. Dynamic alternating current (ac) magnetic measurements between 2.0–13 K reveal that 1 exhibits slow magnetic relaxation under non-zero applied dc fields, being thus a new example of field-induced SIM with easy-plane magnetic anisotropy. Theoretical calculations by CASSCF/NEVPT2 on 1 support the results from magnetometry. The relaxation of the magnetization occurs in the ground state under external dc fields through a two-phonon Raman process and one intra-Kramers mechanism. Full article

The utilisation of miniature robots has become essential in the domain of minimally invasive surgery and long-distance delivery of nanomedicine. Among these, the miniature magnetic continuum robot (MCR) stands out because of its simple structure and dexterity, which allow it to penetrate small cavities, transport specialised tools such as a laser, and deliver medications to support surgical treatment. Nevertheless, because of their soft bodies with a single stiffness, conventional MCRs have limited controllability when navigating through intricate cavities. To address this limitation, we propose a novel concentric magnetic continuum robot (C-MCR) comprising a concentric magnetic catheter with a guidewire having varying stiffness. The C-MCR allows substantial curvature bending owing to its difference in stiffness, and its detachable nature allows it to have four working modes to adapt to specific application requirements with improved stiffness controllability. Experiments demonstrate the ability of the C-MCR to navigate complex pathways and deliver nanomedicines over long distances to specific areas via its internal channels using a large homemade eight-coil electromagnetic system. The C-MCR offers promising application prospects for the long-distance delivery of tailored nanomedicines because of its simple operation, reduced risks, and larger attainable workspace. Full article

This study investigates the impact of alloying Mn-Al-Ga with 3 at.-% Ni and the stability and formation mechanisms of the $\mathsf{\tau }$ phase and the resulting magnetic properties. The stabilizing effect of Ga on the $\mathsf{\tau }$ phase was verified, and the ternary alloy’s magnetization was measured up to $M_{2T}=482$$\mathrm{k}\mathrm{A} {\mathrm{m}}^{-1}$. The phase transformation from $\mathsf{\gamma }$₂ to $\mathsf{\tau }$ in ternary Mn-Al-Ga was demonstrated microscopically. The solubility limit of Ni into the $\mathsf{\tau }$ phase was exceeded at 3 at.-% and a primitive cubic κ phase formed. The Ni addition stabilized the $\mathsf{\tau }$ phase. The highest magnetization at 2 T for the Mn₅₂Al_39.4Ga_5.6Ni₃ alloy was $M_{2T}=416 \mathrm{k}\mathrm{A} {\mathrm{m}}^{-1}$. A new transformation pathway was demonstrated by first annealing the Mn-Al-Ga-Ni alloy at 800 °C for 24 h, which forms a nearly single κ phase, which is followed by a second anneal at 500 °C for 24 h at which the $\mathsf{\tau }$ phase formed with some remaining κ phase. This is a new transformation mechanism since it involves a phase reaction from κ to τ. The energy product of the Mn-Al-Ga-Ni alloy exceeded that of the ternary Mn-Al-Ga alloy by a factor of 4.5. The κ-phase particles in the Mn-Al-Ga-Ni alloy hinder magnetic domain boundary motion, thus providing a method for magnetic hardening and increasing the energy product. Full article

Ferrites are important magnetic materials used in electronic devices. Nanocomposites of ferrites with TiO₂, SiO₂ and carbon quantum dots have gained recent interest due to their unique advantages, such as high chemical stability, surface-active sites, high specific surface area, non-toxicity, excellent optical properties, and tunable porosity. In the present review, general and adaptable coprecipitation, sol–gel, hydrothermal, solvothermal, and Stöber methods for the fabrication of nanocomposites are discussed. These materials offer the advantage of magnetic recovery and superior photocatalytic performance. The potential of nanocomposites to act as photocatalysts to eliminate organic pollutants and microbes from water is discussed. Mechanisms involved in these applications are also elaborated upon. The review provides a detailed study of recent applications and future perspectives of nanocomposites in sustainable water treatment. Full article

A nano-SiO₂ inorganic insulation layer was coated on the surface of FeSi magnetic powder via in situ fluidised vapour deposition. The surface was then coated with organosilicon resin to form an inorganic/organic double-insulating layer. Post-forming and annealing, a ferrosilicon magnetic powder core was prepared. The effects of organosilicon resin content and pressing pressure on the permeability and loss of the ferrosilicon magnetic core were studied. When the ferrosilicon magnetic core was doubly insulated with SiO₂/silicone resin, the silicone resin content increased, the insulation coating gradually thickens, and the saturation magnetic-induction intensity of the magnet gradually decreases; the density and effective permeability showed a trend of increasing first and then decreasing. Increasing the forming pressure can reduce the loss of the core, thereby improving the performance of the core and increasing the permeability without damaging the double-cladding layer. In the powder with the optimised silicone resin content (1.5 wt.%), the magnetic properties of the magnetic core were maximised after preparation at 1500 MPa followed by heat treatment at 773 K. The saturation magnetisation was 187.5 emu/g and the resistivity and permeability reached 10.5 Ω·cm and 49.6, respectively, at 100 mT and 50 kHz. The total loss was 905 mW/cm³. Full article

We report the continuous argon ions irradiation of itinerant Fe₃GeTe₂, a two-dimensional ferromagnetic metal, with the modification to its transport properties measured in situ. Our results show that defects generated by argon ions irradiation can significantly weaken the magnetization (M) and coercive field ($H_c$) of Fe₃GeTe₂, demonstrating the tunable magnetism of this material. Specifically, at base temperature, we observed a reduction of M and $H_c$ by up to 40% and 62.4%, respectively. After separating the contribution from different mechanisms based on the Tian-Ye-Jin (TYJ) scaling relation, it’s the skew scattering that dominates the contribution to anomalous Hall effect in argon ions irradiated Fe₃GeTe₂. These findings highlight the potential of in situ transport modification as an effective method for tailoring the magnetic properties of two-dimensional magnetic materials, and provides new insights into the mechanisms underlying the tunable magnetism in Fe₃GeTe₂. Full article

This study aimed to determine if diffusion-weighted imaging (DWI) can differentiate between benign and malignant lymph nodes in patients with head and neck cancer. A total of 55 patients with confirmed head and neck cancer and enlarged neck nodes were enrolled and evaluated by two radiologists using a workstation. Lymph nodes were analyzed using 3D regions of interest (ROIs) placed on T2-weighted images and compared to the corresponding DWI images. This study found that DWI and ADC values can be used to assess metastatic lymph nodes in the neck and that the sensitivity, specificity, and AUC of a narrower ROI for recognizing metastases were greater compared to the ADC value of the whole node. The study also found that the size of the ROI affects ADC values. The results suggest that DWI can accurately predict the status of cervical lymph nodes in patients with head and neck cancer and that it may be useful in diagnosing, determining the stage, developing a treatment plan, and monitoring these patients. Full article

A hybrid electromagnetic nanomaterial, which is a matrix based on a conjugated polymer of poly-3-amine-7-methylamine-2-methylphenazine with dispersed magnetite nanoparticles immobilized on multi-walled carbon nanotubes, has been synthesized. In situ magnetometry was used to study the kinetics of the hydrogen reduction of Fe${}_3$O${}_4$ immobilized in the structure of a ternary nanocomposite in magnetic fields of different intensities. An increase in the magnetite reduction reaction rate with the formation of metallic iron nanoparticles at $T=420{}^{\circ }$C and at a magnetic field strength in the range of 60–3000 Oe was observed. The dependence of the degree of conversion of Fe${}_3$O${}_4$ on the magnetic field strength was established. Full article