Application Of Magnetic Materials Research Articles

Doping effects in strontium hexaferrite: Theoretical and experimental analysis

Hexagonal ferrites based on SrFe12O19 (SFO) are vital materials in the field of permanent magnets, valued for their cost-effectiveness and reliable magnetic properties, making them a more affordable alternative to rare-earth permanent magnets. This study focuses on understanding the doping effects of commonly used elements in SFO system. DFT calculation results show that doping La or La-Co can enhance the phase stability of SFO, in which Co has a preference for the 4f1 sites of Fe. The total magnetic moment was observed to slightly decrease with La doping, whereas it exhibited an increasing trend with La-Co and La-Ca-Co co-doping and the largest increase of 6.5 % can be obtained in Sr2LaCaFe44Co4O76 (SLCFCO). The increase in the total magnetic moment is mainly attributed to the smaller antiferromagnetic moment of Co than that of Fe on 4f1 sites, as well as the reduction in the antiferromagnetic Fe moments at 4f1 and 4f2 sites. The total density of states indicates a transition from semiconductor behavior to a metallic character both in the La-Co and La-Ca-Co doped versions. The experimental results validate the theoretical predictions, confirming enhancements in magnetic performance. The saturation magnetization increased from 63.86 Am2/kg in SrFe11.7O19 (SFO) to 67.53 Am2/kg in Sr0.4La0.4Ca0.2Fe10.5Co0.5O19 composition. These findings provide a vital understanding of tuning the magnetic and electronic properties in doped SFO, which will enable the development of advanced applications in magnetic materials.

Tuning Valence Tautomerism in Dinuclear Cobalt Complexes by Modulating Communication in the Bridging Ligand

AbstractThe capability of bis(dioxolene) ligands to access multiple redox states makes them ideal candidates to tune the electronic properties of metal complexes, for example to achieve valence tautomerism (VT). In this study, a family of dinuclear cobalt complexes have been isolated with the bridging bis(dioxolene) thean− ligand in the cat2−‐cat2−, cat2−‐SQ⋅− and SQ⋅−‐SQ⋅− states (cat2−=catecholate, SQ⋅−=semiquinonate): [{CoIII(tpa)}2(theacat−cat)](PF6)2 (1), [{CoIII(tpa)}2(theacat−SQ)](PF6)3 (2), and [{CoIII(tpa)}2(theaSQ−SQ)](PF6)4 (3) (theaH4=2,3,6,7‐tetrahydroxy‐9,10‐dimethyl‐9,10‐dihydro‐9,10‐ethanoanthracene, tpa=tris(2‐pyridylmethyl)amine). Multi‐technique analysis confirms that 1, 2 and 3 adopt low spin‐CoIII containing {CoIII‐cat‐cat‐CoIII}, {CoIII‐cat‐SQ‐CoIII} and {CoIII‐SQ‐SQ‐CoIII} states, respectively. Compound 1 undergoes thermally‐induced {CoIII‐cat‐cat‐CoIII} ⇌ {CoIII‐cat‐SQ‐CoII} VT in the solid‐ and solution‐states above 300 K, involving high spin‐CoII. This interconversion is contrary to expectations, as tpa typically stabilizes low spin‐CoIII‐catecholate. Compound 2 is mixed‐valence class II/II–III, indicating a localized electronic structure, with electron transfer faster than the EPR and solvent rearrangement timescales, but slower than the infrared timescale. Compound 3 exhibits strong antiferromagnetic exchange. The overlap between the dioxolene π‐orbitals in thean− increases the accessibility of the cat2−‐SQ⋅− state, resulting in VT for 1. This study demonstrates that thean− can be isolated in multiple oxidation states in metal complexes, which is promising for applications in magnetic materials.

Current Application of Magnetic Materials in the Dental Field

Integrating magnetic materials into dentistry has emerged as a promising advance for addressing diverse dental conditions. Magnetic particles comprising a magnetic core encapsulated within a biocompatible coating offer precise manipulation through external magnetic fields, rendering them invaluable in targeted drug delivery, magnetic resonance imaging, hyperthermia therapy, and diagnostic assays. Their tunable properties allow optimization for specific applications, enhancing therapeutic efficacy while minimizing off-target effects. Additionally, pre-adjust magnets showcase exceptional magnetic field strength and energy density. Their utilization in dental implants and orthodontic treatments facilitates tissue engineering and tooth movement, augmenting clinical outcomes and patient comfort. This review synthesizes current research directions and clinical applications of magnetic materials in dentistry, offering insights into their potential to transform dental healthcare and enhance patient well-being.

Magnetic Material in Triboelectric Nanogenerators: A Review.

Nowadays, magnetic materials are also drawing considerable attention in the development of innovative energy converters such as triboelectric nanogenerators (TENGs), where the introduction of magnetic materials at the triboelectric interface not only significantly enhances the energy harvesting efficiency but also promotes TENG entry into the era of intelligence and multifunction. In this review, we begin from the basic operating principle of TENGs and then summarize the recent progress in applications of magnetic materials in the design of TENG magnetic materials by categorizing them into soft ferrites and amorphous and nanocrystalline alloys. While highlighting key role of magnetic materials in and future opportunities for improving their performance in energy conversion, we also discuss the most promising choices available today and describe emerging approaches to create even better magnetic TENGs and TENG-based sensors as far as intelligence and multifunctionality are concerned. In addition, the paper also discusses the integration of magnetic TENGs as a power source for third-party sensors and briefly explains the self-powered applications in a wide range of related fields. Finally, the paper discusses the challenges and prospects of magnetic TENGs.

Application of Magnetic Materials Combined with Echo® Mass Spectrometry System in Analysis of Illegal Drugs in Sewage.

The aim of this study is to solve the problems of the complicated pretreatment and high analytical cost in the detection technology of trace drugs and their metabolites in municipal wastewater. A high-performance magnetic sorbent was fsynthesized for the enrichment of trace drugs and their metabolites in wastewater to develop a magnetic solid-phase extraction pretreatment combined with the acoustic ejection mass spectrometry (AEMS) analytical method. The magnetic nanospheres were successfully prepared by magnetic nanoparticles modified with divinylbenzene and vinylpyrrolidone. The results showed that the linear dynamic range of 17 drugs was 1-500 ng/mL, the recovery was 44-100%, the matrix effect was more than 51%, the quantification limit was 1-2 ng/mL, and the MS measurement was fast. It can be seen that the developed magnetic solid-phase extraction (MSPE) method is a good solution to the problems of the complicated pretreatment and analytical cost in the analysis of drugs in wastewater. The developed magnetic material and acoustic excitation pretreatment coupled with mass spectrometry analysis method can realize the low-cost, efficient enrichment, and fast analysis of different kinds of drug molecules in urban sewage.

Elucidating the Lithiation Process in Fe3-δO4 Nanoparticles by Correlating Magnetic and Structural Properties.

Due to their high potential energy storage, magnetite (Fe3O4) nanoparticles have become appealing as anode materials in lithium-ion batteries. However, the details of the lithiation process are still not completely understood. Here, we investigate chemical lithiation in 70 nm cubic-shaped magnetite nanoparticles with varying degrees of lithiation, x = 0, 0.5, 1, and 1.5. The induced changes in the structural and magnetic properties were investigated using X-ray techniques along with electron microscopy and magnetic measurements. The results indicate that a structural transformation from spinel to rock salt phase occurs above a critical limit for the lithium concentration (xc), which is determined to be between 0.5< xc ≤ 1 for Fe3-δO4. Diffraction and magnetization measurements clearly show the formation of the antiferromagnetic LiFeO2 phase. Upon lithiation, magnetization measurements reveal an exchange bias in the hysteresis loops with an asymmetry, which can be attributed to the formation of mosaic-like LiFeO2 subdomains. The combined characterization techniques enabled us to unambiguously identify the phases and their distributions involved in the lithiation process. Correlating magnetic and structural properties opens the path to increasing the understanding of the processes involved in a variety of nonmagnetic applications of magnetic materials.

Spin wave resonance frequency in ferromagnetic thin film with the biquadratic exchange interaction

Spin wave resonance (SWR) frequency in ferromagnetic thin film with the biquadratic exchange interaction, interlayer exchange coupling, film thickness, surface anisotropy field, and the external magnetic field has been investigated by using the linear spin-wave approximation and Green’s function techniques. In comparison to previous studies without considering the biquadratic exchange interaction, the SWR frequency behaviors of the energetically mid-higher modes were found to be highly sensitive to biquadratic exchange interaction. SWR frequencies of all modes are linearly proportional to external magnetic field. However, the SWR frequency has nonlinear dependence on the interlayer exchange coupling and surface anisotropy field. Moreover, the biquadratic exchange interaction enabled a considerable improvement in the effects of surface anisotropy field, interlayer exchange coupling, and external magnetic field on SWR frequency. Our results also reveal that a decrease in the SWR frequency of the corresponding mid-lower modes as the thickness of film is increased while the almost the same frequency gap between the energetically highest mode and lowest mode is obtained for the thicker film. These results could help improve the understanding of magnetic properties and promote magnetic materials applications in spintronic devices.

Web-Based Interactive Learning Medium to Foster Students' Understanding on Magnetic Theory Using the Tutorial Method

Technology, particularly in the form of web-based learning resources, aided education during the COVID-19 outbreak. In responding to the condition, this study aims to (1) develop a web-based interactive learning medium application of magnetic material with tutorial method; (2) describe the feasibility of a web-based interactive learning medium for students using magnetic material and a teaching technique. The model used in this study was the ADDIE model. Total of 29 students junior high school in Banjarmasin participated in this study as subject for implementation product. Data collection techniques in this study used validity assessments, questionnaires and tests. The results of the study showed that: (1) HTML, CSS, Javascript, JSON, and Firebase were utilized in the development, and (2) based on these findings, it can be stated that a web-based interactive learning medium for students using magnetic material and the tutorial approach is feasible for use in learning since it meets the the criteria of validity, practicality and effectiveness.

Web-Based Interactive Learning Medium to Foster Students' Understanding on Magnetic Theory Using the Tutorial Method

Technology, particularly in the form of web-based learning resources, aided education during the COVID-19 outbreak. In responding to the condition, this study aims to (1) develop a web-based interactive learning medium application of magnetic material with tutorial method; (2) describe the feasibility of a web-based interactive learning medium for students using magnetic material and a teaching technique. The model used in this study was the ADDIE model. Total of 29 students junior high school in Banjarmasin participated in this study as subject for implementation product. Data collection techniques in this study used validity assessments, questionnaires and tests. The results of the study showed that: (1) HTML, CSS, Javascript, JSON, and Firebase were utilized in the development, and (2) based on these findings, it can be stated that a web-based interactive learning medium for students using magnetic material and the tutorial approach is feasible for use in learning since it meets the the criteria of validity, practicality and effectiveness.

Magnetic Properties of Nanosized Fe and FeCo Systems on Trenched Mo Templates

The manipulation of magnetic anisotropy represents the fundamental prerequisite for the application of magnetic materials. Here we present the vectorial magnetic properties of nanostructured systems and thin films of Fe and FeCo prepared on linearly trenched Mo templates with thermally controlled periodicity. The magnetic properties of the nanosystems are engineered by tuning the shape, size, thickness, and composition parameters of the thin films. Thus, we control coercivity, magnetization, orientation of the easy axis of magnetization, and the long-range magnetic order of the system in the function of the temperature. We distinguish magnetic components that emerge from the complex morpho-structural features of the undulating Fe or FeCo nanostructured films on trenched Mo templates: (i) assembly of magnetic nanowires and (ii) assembly of magnetic islands/clusters. Uniaxial anisotropy at room temperature was proven, characterized, and explained in the case of all systems. Our work contributes to the understanding of magnetic properties necessary for possible further applications of linear systems and undulated thin films.

Electron-beam-evaporation-based multi-source oxide MBE as a synthesis method for high-quality and novel magnetic materials—beyond 3d transition metal compounds

Magnetism and magnetic materials are among the most extensively studied research topics in condensed matter physics. While many practical applications of magnetic materials have been already launched, including permanent magnet motors, magnetic heads in hard disc drives (HDDs), and magnetoresistive random access memories (MRAMs), further search for new magnetic materials has not lost its charm. Here, we show that a multi-electron gun MBE apparatus for oxides, equipped with a high precision rate control system enables the synthesis of well-known ferromagnetic oxides, e.g., SrRuO3 of unparalleled quality. Furthermore, this method also allows to fetch novel magnetic materials, e.g., Sr3OsO6, that are well outside of the synthesis conditions known from 3d transition metal oxides.

Preparation and Application of Magnetic Water Treatment Materials Based on Iron Sludge

In recent years, solid waste iron sludge (red mud, iron-containing water treatment residues, and iron-rich sludge) has been widely used to remove pollutants in the water environment; however, the difficulty of separating powdered iron sludge from the water environment media makes it impossible to apply it as a water treatment material on a large scale, and preparing iron sludge into magnetic materials that are easy to be separated is one of the effective strategies to solve this bottleneck. According to the existing research on iron sludge-based magnetic materials at home and abroad, the preparation methods of magnetic materials using iron sludge as raw materials are summarized, including a series of methods, including the thermal decomposition method, hydrothermal and solvothermal method, co-precipitation method, reduction roasting method, and carbonization method. Additionally, it is pointed out that the currently commonly used preparation methods are thermal decomposition, hydrothermal and solvothermal, and co-precipitation. In addition, the performance and application of these magnetic materials as adsorbents or catalysts in water treatment are also summarized. In general, iron sludge-based magnetic materials can better absorb heavy metals and organic pollutants in water. The main adsorption mechanisms are complexation, electrostatic interaction, reduction, cation exchange, and precipitation. As a catalyst, it can efficiently oxidize and degrade organic pollutants by generating strong oxidizing substances:SO4-· and ·OH. Although there have been many studies on the preparation and application of iron sludge-based magnetic materials, because the raw material iron sludge contains many impurities, the magnetic materials prepared from iron sludge also have certain impurities. Therefore, it is still necessary to strengthen the research on the safety of iron sludge-based magnetic materials in the future to further ensure that they can be used as environmentally friendly materials for water environment restoration.

Classification of magnetic ground states and prediction of magnetic moments of inorganic magnetic materials based on machine learning

Magnetic materials are important basic materials in the information age. Different magnetic ground states are the prerequisite for the wide application of magnetic materials, among which the ferromagnetic ground state is a key requirement for future high-performance magnetic materials. In this paper, machine learning is used to study the classification of ferromagnetic, antiferromagnetic, ferrimagnetic and paramagnetic ground states of inorganic magnetic materials and the prediction of magnetic moments of inorganic ferromagnetic materials. We obtain 98888 inorganic magnetic materials data from the Materials Project database, containing material ids, chemical formulae, CIF files, magnetic ground states and magnetic moments, and extract 582 elemental and structural features for the inorganic magnetic materials by using Matminer. We design a two-step feature selection method. In the first step, RFECV is used to evaluate material features one by one to remove redundant features without degrading the model accuracy. In the second step, we rank the material features to further refine and select the most important material features for the model, and 20 material features are selected for the classification of magnetic ground states and the prediction of magnetic moments, respectively. Among the selected material features, it is found that the electronegativity, the atomic own magnetic moment and the number of unfilled electrons in the atomic peripheral orbitals all make important contributions to the classification of magnetic ground states and the prediction of magnetic moments. We build a magnetic ground state classification model and a magnetic moment prediction model by using the random forest, and quantitatively evaluate the machine learning models by using the 10-fold cross-validation approach, and the results show that the constructed machine learning models has sufficient accuracy and generalization capability. In the test set, the magnetic ground state classification model has an accuracy of 85.23%, a precision of 85.18%, a recall of 85.04%, and an F1 score of 85.24%; the magnetic moment prediction model has a goodness-of-fit of 91.58% and an average absolute error of 0.098 μ&lt;sub&gt;B&lt;/sub&gt; per atom. This study provides a new method and choice for high-throughput classification and screening of magnetic ground states of inorganic magnetic materials and predicting the magnetic moment of ferromagnetic materials.

Effect of bismuth doped Ni-Zn nanoferrite on structural and magnetic properties

The citrate precursor method was used to investigate bismuth substituted Ni-Zn nanoferrites with content Ni0.5Zn0.5BixFe2-xO4 having step size 0.02. Bismuth was incorporated to Ni-Zn spinel ferrite in order to customize its properties. The XRD, VSM determined the structural and magnetic properties of the synthesized samples. The average crystallite size was determined to be between 15 and 28 nm. Except at x = 0.06, a tensile strain was found with a rise in bismuth content using the Williamson-Hall method. The dislocation density was found from 2.95 × 10−3 to 8.22 × 10−3 Å−2. The value of saturation magnetization varies from 57 to70 emu/g and retentivity was in the range 5 to17 emu/g. The squareness ratio of the prepared Bi doped nanoferrites sample has value less than 0.5 which reveals the single domain nature of the prepared materials. This occurrence of uniaxial anisotropy concluded that these ferrites can be used in microwave-absorbing and permanent magnetic material applications.

Effects of nitriding and Ni doping for the frequency of domain wall resonance peak and high-frequency magnetic performance of easy-plane Y2Fe17

Rare earth soft magnetic alloys have potential in high frequency applications due to strong easy-plane anisotropy. As the research progressed, a new resonance peak in the MHz frequency band, the domain wall resonance peak was observed, which seriously affects applications of magnetic materials in power device. A way to decrease it is by increasing domain wall resonance frequency (fdw). In this paper, the composites of easy-plane Y2Fe17 and polyurethane were presented and the easy-plane Y2Fe17 were treated by nitriding and doping. It is found that both nitriding and doping are effective in increasing the permeability. And the frequency of domain wall resonance peaks is varied due to the variation in exchange interaction by nitriding and doping. These results provide insight into soft magnetic properties of soft magnetic composites (SMCs) in the MHz frequency band, particularly for SMCs in power devices applications.

Advances in Processing, Manufacturing, and Applications of Magnetic Materials

Advances in Processing, Manufacturing, and Applications of Magnetic Materials

External Magnetic Field-Enhanced Supercapacitor Performance of Cobalt Oxide/Magnetic Graphene Composites

Abstract The effect of an external magnetic field on the supercapacitor performance of cobalt oxide/magnetic graphene composites has been investigated. The composites were prepared via the hydrothermal reaction of cobalt nitrate with iron oxide-incorporated magnetic graphene. Cobalt oxide nanoparticles were deposited on the graphene sheets and contributed to enhancing the electrochemical capacitance, since the cobalt oxide could work as pseudocapacitance material different from the graphene sheet with the electric double-layer capacitance effect. Further enhancement was observed upon applying the external magnetic field, which was increased via a home-made electric circuit. The specific capacitances of the composite materials under the external magnetic field of 1191 Gauss were found to be a maximum of 11 times higher than those without the magnetic field. It was also suggested that the increase in specific capacitance under the magnetic field follows the power law of the magnetic field due to a magnetohydrodynamic effect. These results demonstrate the importance of the external magnetic field to develop new technologies on energy-related applications of magnetic materials.

Potential suitability of NiO-CuO nanocomposite for photoconductive sensor, soft magnetic materials applications and as antimicrobial agent

Semiconductor nanocomposites containing two metal oxides with different functionalities have gained significant attention as they exhibit improved optical, electrical, magnetic and catalytic properties better than their single entities. The present work aims to synthesize NiO-CuO nanocomposite and to study its suitability for photoconductive sensor, soft magnetic materials applications and as antimicrobial agent. NiO, CuO and NiO-CuO nanoparticles were synthesized by precipitation method. X-ray diffraction (XRD) studies reveal the existence of cubic and monoclinic structured peaks of NiO and CuO in the nanocomposite. Ni-O and Cu-O related bands were observed from the Fourier Transform Infrared (FTIR) spectrum of the nanocomposite. The nanocomposite exhibits band gap between NiO and CuO. Photosensitivity of NiO improves when coupled with CuO. The nanocomposite possess enhanced ferromagnetic behaviour due to increased point defects, uncompensated spins and exchange coupling between Cu2+ and Ni2+ ions. CuO improved the antifungal ability of NiO against Aspergillus terreus (A. Terreus) fungi.

(Zn + Co) co-doped CdO thin films with improved figure of merit values and ferromagnetic orderings with low squareness ratio well suited for optoelectronic devices and soft magnetic materials applications

The present study focuses on the suitability of CdO thin films towards optoelectronic and spintronic devices through (Zn + Co) co-doping. Para to ferromagnetic transition mediated by oxygen vacancies takes place in the CdO:Zn thin films through Co doping which was acknowledged from the photoluminescence studies. Defect level peaks observed in the PL spectra at 411, 460 and 494 nm are associated with metal interstitials (Cdi, Zni, Coi), singly ionized oxygen vacancies (Vo+) and oxygen vacancies (Vo), respectively. The deep-level or trap state emission due to the ionized oxygen vacancies is observed at 521 nm. XRD analysis indicate that the undoped, Zn-doped (CdO:Zn) and (Zn + Co) co-doped CdO thin films have cubic structure with (1 1 1) plane being the preferential one. The crystallite size of pure CdO decreases with Zn-doping and with Co co-doping it increases. Cauliflower shaped nanostructures are evinced for the (Zn + Co) co-doped films. Increased optical transparency and decreased sheet resistance were observed for the (Zn + Co) co-doped films. Increased Haacke’s quality factor observed for the (Zn + Co) co-doped films confirmed their potential for optoelectronic devices.

Temperature scaling of two-ion anisotropy in pure and mixed anisotropy systems

Magnetic anisotropy plays an essential role in information technology applications of magnetic materials, providing a means to retain the long-term stability of a magnetic state in the presence of thermal fluctuations. Anisotropy consists of a single-ion contribution stemming from the crystal structure and two-ion terms attributed to the exchange interactions between magnetic atoms. A lack of robust theory crucially limits the understanding of the temperature dependence of the anisotropy in pure two-ion and mixed single-ion and two-ion systems. Here, we use Green's function theory and atomistic Monte Carlo simulations to determine the temperature scaling of the effective anisotropy in ferromagnets in these pure and mixed cases, from saturated to vanishing magnetization. At low temperature, we find that the pure two-ion anisotropy scales with the reduced magnetization as $k(m) \sim m^{2.28}$, while the mixed scenario describes the diversity of the temperature dependence of the anisotropy observed in real materials. The temperature dependence of the mixed anisotropy determined here is expected to considerably contribute to the understanding and the control of the thermal properties of magnetic materials.