Magnetic Materials Research Articles

Hybrid CoFe2O4-CNTs-graphene: Synthesis and characterization for energy storage devices

Hybrid materials play a crucial role in a spectrum of energy storage devices. Among them CoFe2O4–CNT–graphene hybrid stands out as versatile magnetic materials with wide-ranging applications spanning electronics, magnetism, and sensor industries. In this study, we synthesized CoFe2O4–CNT–graphene hybrid utilizing ultrasonication method. This fabrication method resulted in the formation of CoFe2O4 nanoparticles, along with bamboo-like carbon nanotubes (CNTs) and graphene nanosheets which collectively establish an open three-dimensional structure. Thorough analyses were conducted on the synthesized nano-composites employing various characterization techniques such as XRD, FT-IR, Raman and FESEM. Further characterization through XPS confirmed the formation of spinel ferrites, detecting the presence of carbon sp2, C1s, carboxylates (O-C-OH), and sp3 carbon, indicating the presence of carbon‑carbon (CC) bonds and confirms the energy levels of Co2p1/2 and Co2p3/2 indicating the effective incorporation of CFO onto the CNT/graphene surface. Analysis of dielectric parameters revealed promising characteristics for high-frequency devices, attributed to low dielectric loss, high quality factor, short relaxation time, and diverse responses exhibited by these materials. The M–H loops of the composite samples displayed ferromagnetic hysteresis behavior due to the presence of ferrite in the matrices. The coercivity value shows a slight improvement in the hybrid samples, while saturation magnetization values decrease, indicating a 1:1 weight ratio of ferrite particles to the host matrix with the incorporation of nonmagnetic CNTs and graphene, and the Hc value increases with the addition of these carbon-based materials due to increased surface anisotropy energy. Upon evaluation of dielectric and magnetic properties the hybrid materials demonstrated an enhanced dielectric and magnetic properties which render these materials suitable for utilization across a spectrum of energy storage devices.

Magneto-electronic and optoelectronic attributes of half-Heusler VXPt (X = Br, Se) alloys: A first-principles study

High-spin polarized magnetic materials might be useful in spintronics applications. The spin-polarized magnetic, optical, electronic and structural attributes of half-Heusler VXPt (X = Br, Se) alloys were theoretically explored and calculated using the WIEN2k code. The ground states of the structures are optimized, and the bulk moduli and lattice constants are computed. The values obtained from the formation energies show their stability. For VBrPt, an energy gap is present in major and minority spin carriers, while for VSePt, major spin carriers exhibit an energy gap and metallic character is seen in minority spin carriers. The band structures are further illustrated deeply through the investigation of density of states. The electron density graphs depict the ionic bonding in both alloys. The magnetic moments are additionally assessed, and the recorded values support the magnetic characteristics of VBrPt and VSePt. The assessment of how the studied alloys react to light is determined by computing various parameters. The imaginary component and absorption coefficient anticipate substantial light absorption within the visible region. The calculated outcomes unveiled the potential of the examined alloys for applications in spintronics.

Numerical study on induction heating enhanced methanol steam reforming for hydrogen production

Electromagnetic induction heating technology, characterized by its non-contact thermal heat transfer, diminished thermal inertia, and facile temperature management, is applied in this study to enhance catalytic methanol steam reforming (MSR) reaction process. A two-dimensional reactor model was developed integrating electromagnetic field coupling with MSR reactions, fluid dynamics and heat transfer. In the reactor, heat is induced instantaneously on the magnetic material through an electromagnetic induction process, which generated by renewable electricity. Results showed that the Internal - Double Row Cylinder (IN-DRC, cylinder means that the shape of induction heating element is cylindrical.) highest heating efficiency is 38.3%, which is limited by the kinetics of MSR reaction. Here, thermal efficiency reaches its maximum with the reaction channel outlet temperature reaching about 580 K. Internal - Double Row Cylinder (IN-DRC) and Internal - Double Row Ball (IN-DRB, ball means that the shape of induction heating element is spherical) methanol conversions are virtually identical, with a maximum value close to 100%. Furthermore, the findings that the adoption of internal induced heating, in contrast to external heating, across the four reactor designs can effectively mitigate temperature gradient within the reactors. This reduction in thermal disparity significantly amplifies methanol conversion within the reactor, thereby markedly enhancing its overall performance in hydrogen production.Therefore, non-contact internal induction heating method has the potential for substantially hydrogen production processes.

Ti3C2Tx/Ni0.2Mn0.4Zn0.4Fe2O4 ferrite nanocomposites: Dual-loss mechanism with engineered composition for microwave absorption

Ni0.2Mn0.4Zn0.4Fe2O4 (NMZF) nanoparticles were anchored on the surface of MXene(Ti3C2Tx) to form Ti3C2Tx/NMZF nanocomposites for optimization of microwave absorption performance. The Ti3C2Tx/NMZF nanocomposites were synthesized by using a four-step strategy, including sonication, stirring, hydrothermal reduction and vacuum drying. More than 40 percent of the NMZF nanoparticles in this nanocomposite were assembled to form a conductive network. Meanwhile, the multilayer MXene acted as a framework to host the NMZF nanoparticles, providing dipolar polarization, interfacial polarization and eddy current loss. Benefiting from the structure design of MXene, combined with magnetic materials and optimized impedance matching, the Ti3C2Tx/NMZF exhibited a minimum reflection loss (RLmin) of −57.39 dB, with a thickness of 2.97 mm and an effective absorption bandwidth (EAB) of 3.2 GHz. Therefore, such a facile method could be used to construct nanocomposites with microwave absorption performance (-57.39 dB, 3.2 GHz), so as to address microwave pollution issues.

Rapid screening of xanthine oxidase inhibitors from Ligusticum wallichii by using xanthine oxidase functionalized magnetic metal-organic framework.

In this study, xanthine oxidase was immobilized for the first time using a novel magnetic metal-organic framework material (Fe3O4-SiO2-NH2@MnO2@ZIF-8-NH2). A ligand fishing method was established to rapidly screen XOD inhibitors from Ligusticum wallichii based on the immobilized XOD. Characterization and properties of the immobilized enzyme revealed its excellent stability and reusability. A ligand was screened from Ligusticum wallichii and identified as ligustilide by ultra-high performance liquid chromatography tandem mass spectrometry. The IC50 value of ligustilide was determined to be 27.70 ± 0.13μM through in vitro inhibition testing. Furthermore, molecular docking verified that ligustilide could bind to amino acid residues at the active site of XOD. This study provides a rapid and effective method for thepreliminary screening of XOD inhibitors from complex natural products and has great potential for further discovery of anti-hyperuricemic compounds.

Meta Analysis of the Effect of Applying the Problem Based Learning Model in Physics Learning to Improve Students' Ability to Solve Problems

The meta-analysis method in this research was used to determine how problem-based learning activities influence problem-solving abilities. Analysis is carried out based on material units and levels/classes. Based on the results of the analysis, it was found that the mechanical material unit had an effect size of 0.83 in the high category, for the electric magnetic material unit it had an effect size value of 1.12 in the very high category, for the optical wave material unit it had an effect size of 1.66 with very high category, for thermodynamic material units it has an effect size of 1.41 in the very high category, and for fluid material units it has an effect size of 1.56 in the very high category. Then for class X it has an effect size of 1.19 in the very high category, for class XI it has an effect size of 1.35 in the very high category and for class In conclusion, for the optical wave material unit, it has an effect size of 1.81 which has a very high influence on students' ability to solve problems and for class XI level it has an effect size of 1.35 which has a very high influence on students' ability to solve problems.

Effect of microwave sintering on density, microstructural and magnetic properties of pure strontium hexaferrite at low temperatures and heating rate

In recent decades, the rising demand for permanent magnetic materials has driven manufacturers to explore substitutes for rare earth elements in response to their fluctuating prices and negative environmental impact. M-type hexaferrites considered as good alternatives and studies have focused on enhancing their magnetic and structural properties through various approaches. In this study, new approach using low heating rate microwave sintering has been applied to investigate the changes on density, microstructure, and magnetic properties of strontium hexaferrite from core to surface. Sintering temperatures of 950 °C, 1000 °C, 1050 °C, and 1100 °C with 10 °C/minute heating rate were applied accordingly. The bulk density, FESEM, XRD and VSM tests were conducted to study materials’ properties. The outcomes of the study showed exponential relationship between density and sintering temperature reaching optimum value of 91.4 % at 1050 °C and then declined slightly at observed to analysis confirmed the magnetoplumbite structure P63/mmc in all samples and high crystallized structure at 1050 °C, with the occurrence of α-Fe2O3 at 1100 °C. Grain growth and crystallization observed to increase at higher sintering temperature with agglomeration while denser and melted boundaries at lower temperatures. Magnetic properties especially remanence magnetization Mr and saturation magnetization Ms fluctuated with sintering temperature achieving optimum values of 28.188 emu/g and 55.622 emu/g at 1000 °C respectively. Coercivity Hc and magnetic energy density BH max recorded optimum values at 1050 °C. The findings emphasize the critical role of microwave sintering in tailoring the properties of strontium hexaferrite for magnetic applications.

Revisiting Rare Earth Permanent Magnetic Alloys of Nd-Fe-C

Nd-Fe-C alloys have been reported as hard magnetic materials with a potential higher coercivity than Nd-Fe-B alloys. However, it has been seldom studied since its intrinsic properties were investigated in the last century. Here, we revisited the structure, phase precipitation and magnetic properties of rapidly quenched ternary Nd-Fe-C alloys for further understanding their composition-microstructure-property relationships. The Nd10+xFe84−xC6 (x = −2, 0, 2, 3, 4, 5) alloys with various compositions were prepared by melt spinning. The results show that the hard magnetic Nd2Fe14C phase can be hardly formed in the as-spun alloys. Instead, the alloys are composed of soft magnetic α-Fe phase and planar anisotropic Nd2Fe17Cx phase. After annealing above 650 °C, the Nd2Fe14C phase is precipitated by the peritectoid reaction. All optimally annealed alloys contain Nd2Fe14C and Nd2Fe17Cx phases, while the presence and content of α-Fe phase are determined by the alloy composition. The crystallization degree of the as-spun alloys has an effect on their magnetic properties after annealing. After the annealing treatment, partly crystallized as-spun alloys exhibit better magnetic properties than the amorphous alloys. The intrinsic coercivity Hcj = 847 kA/m, remanence Jr = 0.69 T, and maximum energy product (BH)max = 64.3 kJ/m3 were obtained in the Nd14Fe80C6 alloy annealed at 725 °C. The formation of the Nd2Fe14C and Nd2Fe17Cx phases with the Nd2O3 phase precipitated at the triangular grain boundaries is responsible for its relatively good properties. Although the magnetic properties of Nd-Fe-C alloys obtained in this work are inferior to those of Nd-Fe-B, the present results help us to further understand the magnetic behavior of Nd-Fe-C alloys.

Unraveling the electronic structure and magnetic transition evolution across monolayer, bilayer, and multilayer ferromagnetic Fe3GeTe2

Two-dimensional (2D) van der Waals (vdW) magnets have sparked widespread attention due to their potential in spintronic applications as well as in fundamental physics. Ferromagnetic vdW compound Fe3GeTe2 (FGT) and its Ga variants have garnered significant interest due to their itinerant magnetism, correlated states, and high magnetic transition temperature. Experimental studies have demonstrated the tunability of FGT’s Curie temperature, TC, through adjustments in quintuple layer numbers (QL) and carrier concentrations, n. However, the underlying mechanism remains elusive. In this study, we employ molecular beam epitaxy (MBE) to synthesize 2D FGT films down to 1 QL with precise layer control, facilitating an exploration of the band structure and the evolution of itinerant carrier density. Angle-resolved photoemission spectroscopy (ARPES) reveals significant band structure changes at the ultra-thin limit, while first-principles calculations elucidate the band evolution from 1 QL to bulk, largely governed by interlayer coupling. Additionally, we find that n is intrinsically linked to the number of QL and temperature, with a critical value triggering the magnetic phase transition. Our findings underscore the pivotal role of band structure and itinerant electrons in governing magnetic phase transitions in such 2D vdW magnetic materials.

Enhancement in Magnetic and Magnetocaloric Properties of CoFe2O4 Nanofibers at Lower Temperatures

AbstractThis research paper investigates new and first insights into the magnetic and magnetocaloric properties of one-dimensional (1D) cobalt ferrite CoFe2O4 (CFO) nanofibers (NFs) fabricated using a sol–gel-based electrospinning technique, focusing in particular on their behavior at low temperatures for specific applications. The microstructural, structural, magnetic, and magnetocaloric properties of the calcined CFO NFs were explored. The microstructure of the NFs, with an average diameter of 210 nm, was examined by scanning and transmission electron microscopy (SEM, TEM). The x-ray diffraction (XRD) of the CFO NFs showed a pure cubic close-packed (ccp) spinel crystalline structure with the Fd$$\overline{3}$$ 3 ¯ m space group. The Raman spectroscopic studies further confirm the cubic inverse spinel phase. The magnetic properties were explored as a function of temperature, ranging from 10 K to 300 K, and ferromagnetic behavior was observed with the highest saturation magnetization of 75.87 emu/g and coercivity of 723 Oe at room temperature. The variation of the magnetic entropy was measured indirectly using the Maxwell approach with an increasing magnetic field. A maximum of $$\left| {\Delta S} \right|$$ Δ S = 1.71 J/K was reached around 32 K. At 180 K, the associated adiabatic temperature change, ΔTmax, was 0.93 K, with a large RCP value of 7.58 J/kg, which is reasonably high for the corresponding nanoparticles (NPs). This work suggests that 1D CFO NFs offer a promising route for the production of nanostructured magnetic materials, potentially impacting various electronic and electromagnetic device applications at low temperatures.

Modelling PM dipoles with longitudinal field gradient for SILA facility

Computational models are described which were built for parametric simulations of permanent magnet (PM) dipoles with a longitudinal field gradient. The dipoles will be used as bending magnets in the synchrotron facility SILA, a new project of the National Research Center “Kurchatov Institute”. The dipoles employ a Sm-Co permanent magnet material and pure iron. The need for high magnetic performance and anticipated interference between neighbouring components is a challenge for design and construction of the magnet system. For this reason the magnet designs must rely on precision 3D simulations. The dipoles are described in detail with parameterized models. Parametric simulations are to be applied at all stages of the project till the commissioning to provide realistic prediction of the magnet behaviour.

Application of ferromagnetic materials for technological processes thermal regime stabilization (Review)

The research focuses on the technological and auxiliary equipment used in various industries that require maintaining a specific narrow temperature range. The study aims to critically analyze the potential use of structural elements made of ferromagnetic materials with a second-kind phase transition temperature (Curie temperature or Curie point) in high-performance, knowledge-intensive industries, particularly the chemical industry. These materials correspond to the required temperature of the processed or transported liquid or loose medium. The technological processes using the magnetothermal effect and the corresponding designs of equipment are considered: heat exchange, heat and mass exchange, mechanical and hydromechanical, equipment for processing thermoplastics, as well as other devices used in various branches of industry, in particular chemical, food and microbiological, in thermal energy, metallurgy, agriculture, medicine and construction. It is shown that the specified method of ensuring the required thermal regime is suitable for use primarily in large-tonnage continuous production. As the conducted studies have shown, the proposed approach to stabilizing the heat flow of various technological and auxiliary equipment is effective and quite promising. The indisputable advantage of the corresponding method is to ensure a certain temperature of the working parts of the equipment with high accuracy, however, this method is quite difficult to implement on the existing equipment, which is mostly made of magnetic materials (steel, cast iron). Therefore, to implement the proposed method in practice, it is necessary to develop new equipment designs or to subject existing samples to deep modernization. At the same time, there may be difficulties associated with the search for existing or the creation of new ferromagnetic materials with the required thermomagnetic properties for the manufacture of appropriate structural elements of technological and auxiliary equipment. However, in certain cases, the proposed method of maintaining the specified temperature of the processed media may become the most appropriate (primarily in fine chemical technology, biotechnology, pharmaceuticals, precision instrument manufacturing, microelectronics, and medicine).

Synthesis and characterization of Fe3O4@MIL-100 nanoparticles as an SSI-assisted drug carrier

In this study, core–shell structured Fe3O4@MIL-100 nanoparticles were synthesized through an in-situ growth method. The resulting magnetic composite exhibited significant magnetic responsivity, with a magnetization saturation (Ms) of 37.24 emu/g and a magnetocaloric temperature rise of 42.1 ℃ within 6 min at 20 A. Supercritical solution impregnation (SSI) technology was used for CUR loading, achieving an outstanding drug loading content of 4.36 wt% compared to ethanol impregnation. These results show the potential of the present magnetic materials with SSI process in biomedical applications.

Promoting the ordering of L10-FeNi phase via chemical interactions with substrate: A molecular dynamics simulation study

The L10-type FeNi intermetallic phase is an important rare-earth-free magnetic material. However, its fabrication remains challenging. In this paper, we propose a chemical-interaction-enhanced ordering mechanism in vapor deposition processes, which is supported by molecular dynamics deposition simulations. Additionally, we describe guidelines for the fabrication of further ordered intermetallic thin films. Thus, we present not only the fabrication of an L10-type FeNi intermetallic magnet but also guidelines for developing diverse structural and functional layer-ordered intermetallic materials.

Easily reusable g-C3N4/NiFe2O4 magnetic heterojunction material for tetracycline degradation by visible light

To efficiently degrade tetracycline (TC) in water, magnetic reusable g-C3N4/NiFe2O4 heterojunction photocatalyst was synthesized by thermal polymerization and hydrothermal method. The obtained heterojunction photocatalyst achieved efficient degradation by degrading 86 % of TC in 2 h under visible light irradiation. and showed excellent magnetic reusable performance. The heterostructure formed between g-C3N4 and NiFe2O4 improved the separation efficiency and photoresponse range of photogenerated electrons and holes, and thus improved the photocatalytic degradation performance of the material. This study provides a new strategy for the efficient degradation of TC in water under visible light.

Magnetic Phase-Change Microcapsules with High Encapsulation Efficiency, Enhancement of Infrared Stealth, and Thermal Stability

Due to energy shortages and the greenhouse effect, the efficient use of energy through phase-change materials (PCMs) is gaining increased attention. In this study, magnetic phase-change microcapsules (Mag-mc) were prepared by suspension polymerization. The shell layer of the microcapsules was formed by copolymerizing methyl methacrylate and triethoxyethylene silane, with the latter enhancing the compatibility of the shell layer with the magnetic additive. Ferric ferrous oxide modified by oleic acid (Fe3O4(m)) was added as the magnetic additive. Differential scanning calorimetry (DSC) testing revealed that the content of phase-change materials in microcapsules without and with ferric ferrous oxide were 79.77% and 96.63%, respectively, demonstrating that the addition of Fe3O4(m) improved the encapsulation efficiency and enhanced the energy storage ability of the microcapsules. Laser particle size analysis showed that the overall average particle sizes for the microcapsules without and with ferric ferrous oxide were 3.48 μm and 2.09 μm, respectively, indicating that the incorporation of magnetic materials reduced the size and distribution of the microcapsules. Thermogravimetric analysis indicated that the thermal stability of the microcapsules was enhanced by the addition of Fe3O4(m). Moreover, the infrared emissivity of the microcapsule-containing film decreased from 0.77 to 0.72 with the addition of Fe3O4(m) to the shell of microcapsules.

Amine-modified magnetic particles: An efficient tool for enhanced RNA extraction

Magnetic particles are an effective tool for simple, time-saving, and labour-saving nucleic acid extraction. In this study, we investigated the isolation of nucleic acids (NA) using 11 variants of magnetic nanoparticles (MPs, 52 ± 6.8 nm) with a surface concentration of amine groups up to 20.8 nmol · mg−1. All results were compared with morphologically identical magnetic material modified with SiO2 grafted with (3-aminopropyl)triethoxysilane (APTES). The properties of these materials were characterized by transmission electron microscopy, scanning electron microscopy, dynamic and electrophoretic light scattering, and magnetometry. Concentrations of amine groups on MPs-APTES were determined by the chemical bind and release method with photometric quantification.The isolation potential of the proposed materials toward NAs was evaluated using gel electrophoresis with photometric determination of NAs concentrations and RT-qPCR. Our results show that the NAs yields of MPs-APTES are higher than the reference MPs-SiO2, regardless of the amine group concentrations. Although the total yield decreased with the concentration of amine groups, a different affinity towards genomic DNA (gDNA) was observed. A high concentration of grafted amine groups induced a preference for ribosomal RNA (rRNA) over gDNA and mediated effective NA elution. Densitometric image analysis of gDNA bands showed that NAs isolated by MPs-SiO2 contained significantly higher DNA levels than MPs with 1/32 %, 1/2 %, and 16 % APTES modification, which was subsequently confirmed by qPCR. Gene expression analysis performed by RT-qPCR revealed that unwanted gDNA contamination did not significantly affect the threshold cycles (Ct) of target genes when cDNA-specific primers were used, but may lead to overestimation when targeting genes with low expression and no possibility to design cDNA-unique primers. From a practical point of view, MPs-APTES provided better dose-dependent NA isolation performance with stable NA quality.

Effect of Zn-substitution on magnetic structure of cobalt ferrite nanoparticles.

This study investigates the effects of Zn substitution on the magnetic properties of ∼5nm cobalt ferrite nanoparticles (ZnxCo1-xFe2O4, where x = 0, 0.13, 0.34, and 0.55), demonstrating that Zn substitution induces complex changes in spin canting and prompts a redistribution of cations among the sublattices. We reconstructed the magnetic structure of these spinel ferrites by integrating the classical two-sublattice Néel model of ferrimagnetism with the data obtained from 57Fe Mössbauer spectrometry. Consequently, this research provides a comprehensive understanding of how Zn substitution tunes the magnetic properties of CoFe2O4 nanoparticles, offering valuable insights into the development of magnetic materials with tailored properties for various applications.

Optimizing the composition of (Ce,La)(Co,Fe)5for permanent magnet applications using density functional theory.

In this work, we calculated physical quantities, including the magnetocrystalline anisotropy constant (Ku) and magnetization (Ms), for disordered (Ce,La)(Co,Fe)5systems. Based on the results, we propose CeCo4.7Fe0.3as the optimum composition for high-performance permanent magnets. The calculations employed the full-potential Korringa-Kohn-Rostoker Green's function method, and dealt with the compositional disorder of the systems within the coherent potential approximation. It was found that the La doping reducesKuat 0 K but increases the Curie temperature (TC), which leads to improvement of the magnetic properties at high temperatures. CeCo4.7Fe0.3had the largest magnetic anisotropy ofKu= 15.14 MJ/m3, which is larger than that of CeCo5(Ku= 14.77 MJ/m3).TCof CeCo4.7Fe0.3estimated by the mean-field approximation was 1005 K, which exceeds that of CeCo5(965 K). Further, our calculations showed that while doping of Fe destabilizes the system, CeCo4.7Fe0.3is stable against decomposition into the simple substances. We also show calculated data that are informative for exploring high-performance permanent magnet materials in this paper.

Pressure-induced magnetic and topological transitions in non-centrosymmetric MnIn2Te4

In recent years, the study of magnetic topological materials, with their variety of exotic physics, has significantly flourished. In this work, we predict the interplay of magnetism and topology in the non-centrosymmetric ternary manganese compound MnIn2Te4under external hydrostatic pressure, using first-principles calculations and symmetry analyses. At ambient pressure, the ground state of the system is an antiferromagnetic insulator. With the application of a small hydrostatic pressure (∼0.50 GPa), it undergoes a magnetic transition, and the ferromagnetic state becomes energetically favorable. At ∼2.92 GPa, the ferromagnetic system undergoes a transition into a Weyl semimetallic phase, which hosts multiple Weyl points in the bulk. The presence of non-trivial Weyl points have been verified by Wilson bands computations and the presence of characteristic surface Fermi arcs. Remarkably, we discover that the number of Weyl points in this system can be controlled by pressure and that these manifest in an anomalous Hall conductivity (AHC). In addition to proposing a new candidate magnetic topological material, our work demonstrates that pressure can be an effective way to induce and control topological phases, as well as AHC, in magnetic materials. These properties may allow our proposed material to be used as a novel pressure-controlled Hall switch.