Applications In Magnetic Devices Research Articles

Integrating Experimental and Computational Insights: A Dual Approach to Ba2CoWO6 Double Perovskites

Double perovskite materials have emerged as key players in the realm of advanced materials due to their unique structural and functional properties. This research mainly focuses on the synthesis and comprehensive characterization of Ba2CoWO6 double perovskite nanopowders utilizing a high-temperature conventional solid-state reaction technique. The successful formation of Ba2CoWO6 powders was confirmed through detailed analysis employing advanced characterization techniques. Rietveld refinement of X-ray diffraction (XRD) and Raman data established that Ba2CoWO6 crystallizes in a cubic crystal structure with the space group Fm-3m, indicative of a highly ordered perovskite lattice. The typical crystallite size, approximately 65 nm, highlights the nanocrystalline nature of the material. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) discovered a distinctive morphology characterized by spherical shaped particles, suggesting a complex particle formation process influenced by synthesis conditions. To probe the electronic structure, X-ray Photoelectron Spectroscopy (XPS) identified cobalt and tungsten valence states, critical for understanding dielectric properties associated with localized charge carriers. The semiconducting character of the synthesized Ba2CoWO6 nanocrystalline material was confirmed through UV-Visible analysis, which revealed an energy bandgap value of 3.3 eV, which aligns well with the theoretical predictions, indicating the accuracy and reliability of the experimental results. The photoluminescence spectrum exhibited two distinct emissions in the blue-green region. These emissions were attributed to the transitions 3P0→3H4, 3P0→3H5, and 3P0→3H6, primarily resulting from the contributions of Ba2+ ions. The dielectric characteristics of the compound were analyzed across a different range of frequencies, spanning from 1 kHz to 1 MHz. Magnetic characterization using Vibrating Sample Magnetometry (VSM) revealed antiferromagnetic behavior of Ba2CoWO6 ceramics at room temperature, attributed to super-exchange interactions between Co3+ and W5+ ions mediated by oxygen ions in the perovskite lattice. Additionally, first-principles calculations based on the Generalized Gradient Approximation (GGA+U) with a modified Becke–Johnson (mBJ) potential were employed to gain a deeper understanding of the structural and electronic properties of the materials. This approach involved systematically varying the Hubbard U parameter to optimize the description of electron correlation effects. These results deliver an extensive understanding of the structural, optical, morphological, electronic, and magnetic properties of Ba2CoWO6 ceramics, underscoring their potential for electronic and magnetic device applications.

Investigation of structural, magnetic and morphological properties of Zinc and Cobalt-doped Nickel Ferrites

Abstract Nickel Ferrite nanocrystalline material doped with transition metal ions (Zn2+, Co2+) was obtained by chemical combustion method using respective nitrate hexahydrates and glycine as fuel. The phase purity of the prepared ceramic samples was ascertained using Powder X-ray diffraction (XRD) exhibiting an inverse cubic spinel structure with space group Fd 3 ‾ $\overline{\mathrm{3}}$ m. Lattice parameters follow the Vegard law, indicating a consistent lattice expansion. The formation of porous nanocrystalline ferrite was confirmed by Scanning Electron Microscopy (SEM) images and corroborated by Williamson-Hall analysis. Raman Spectroscopic analysis identified characteristic bands corresponding to vibrational modes of nickel ferrite (NiFe2O4) and revealed shifts in the peak position with doping by zinc (Zn) and cobalt (Co). Vibrating Sample magnetometry (VSM) analysis indicated varied magnetic behaviour with different dopants and concentrations highlighting the influence of cation substitution on magnetic properties. The specific saturation magnetization (M s ), remanent magnetization (M r ) and coercivity (H c ) are improved by the substitution of Zn2+ and Co2+ ions. This simple and cost-effective preparation technique holds promise for synthesizing high-quality nickel ferrite, which could find applications in magnetic and electronic devices.

Time-resolved magneto-optical effects in the altermagnet candidate MnTe

α -MnTe is an antiferromagnetic semiconductor with above room temperature TN = 310 K, which is promising for spintronic applications. Recently, it was reported to be an altermagnet, containing bands with momentum-dependent spin splitting; time-resolved experimental probes of MnTe are, therefore, important both for understanding novel magnetic properties and potential device applications. We investigate ultrafast spin dynamics in epitaxial MnTe(001)/InP(111) thin films using pump-probe magneto-optical measurements in the Kerr configuration. At room temperature, we observe an oscillation mode at 55 GHz that does not appear at zero magnetic field. Combining field and polarization dependence, we identify this mode as a magnon, likely originating from inverse stimulated Raman scattering. Magnetic field-dependent oscillations persist up to at least 335 K, which could reflect coupling to known short-range magnetic order in MnTe above TN. Additionally, we observe two optical phonons at 3.6 and 4.2 THz, which broaden and redshift with increasing temperature.

Improvement in magnetic behaviour on Erbium addition to Co-Mn ferrite nanoparticles for magnetic device applications

Magnetic nanoparticles exhibit remarkable and notably unique magnetic characteristics, owing to their high ratio of surface-to-volume and various configurations of crystals. The properties of these nanoparticles are also significantly influenced by their preparation method. In the present work, Er3+ substituted ferrite nanoparticles of Co0.5Mn0.5ErxFe2-xO4 (x = 0, 0.005, 0.01, 0.05, and 0.1) have been synthesized by using an aqueous sol-gel method. The prepared samples have been characterized using XRD, FESEM, RAMAN, FTIR, VSM, and UV-Visible spectroscopy to investigate various physical properties. XRD, RAMAN and FTIR spectroscopy confirm the formation of face centred cubic inverse spinel structure. There is variation in the structural parameters with the substitution of Er3+. The intrinsic vibrations of metal ions at tetrahedral and octahedral sites are observed in the FTIR spectra. Ferrimagnetic behaviour has been obtained for these ferrite nanoparticles. An increase in remanence ratio has been observed with erbium substitution. There is strengthening of A-B super-exchange interaction altering the magnetic characteristics on Er3+ substitution in the Co-Mn ferrites. The same has been corroborated by the suggested cation distribution and the computed values of Yafet-Kittel angles. There is an increase in the value of optical band gap from 3.63 eV (x=0) to 3.85 eV (x=0.1) with Er3+ content. An improvement in saturation magnetization (Ms), coercivity (), and magnetic moment ( have been obtained on addition of Er3+ to Co-Mn ferrites, suggesting their potential application for data storage devices.

Doping dependent magnetic and thermoelectric response of perovskite BaGeO3 for spintronics and energy applications

Using ab-initio simulations, we have investigated the magnetic and thermoelectric response of the pristine and Mn-, Ni-, and In-doped BaGeO3 at Ge-site. The dopants Mn, Ni, and In can be doped at Ge-site due to lower formation energies. The dopants significantly alter the electronics properties of BaGeO3. Interestingly, the In-BaGeO3 exhibits half-metallic nature. Furthermore, our doped system exhibit the magnetic behaviour with 100 % polarization near Fermi level. Additionally, the spin orientation favors the ferromagnetic (FM) states for Mn-BaGeO3. Furthermore, the realization of magnetic anisotropy energy (MAE) may pave the way to use BaGeO3 for applications in magnetic devices. Moreover the zT (0.95) is enhanced for In-BaGeO3. Thus, our studied configuration could potential candidate for thermoelectric insulation as well as thermoelectric cooling applications. We are expecting that our findings could open the ways to utilize the BaGeO3 in the domain of spintronics and magnetic semiconductor devices applications.

Analysis of Magnetization Dynamics in NiFe Thin Films with Growth-Induced Magnetic Anisotropies

We have used angled magnetron sputter deposition with and without sample rotation to control the magnetic anisotropy in 20 nm NiFe films. Ferromagnetic resonance spectroscopy, with data analysis using a Bayesian approach, is used to extract material parameters relating to the magnetic anisotropy. When the sample is rotated during growth, only shape anisotropy is present, but when the sample is held fixed, a strong uniaxial anisotropy emerges with in-plane easy axis along the azimuthal direction of the incident atom flux. When the film is deposited in two steps, with an in-plane rotation of 90 degrees between steps, the two orthogonal induced in-plane easy-axes effectively cancel. The analysis approach enables precise and accurate determination of material parameters from ferromagnetic resonance measurements; this demonstrates the ability to precisely control both the direction and strength of uniaxial magnetic anisotropy, which is important in magnetic thin-film device applications.

Effect of Trivalent Ho3+ Ion Doping on Structural, Magnetic, Optical, and Electrical Properties of BiFeO3 Nanoparticles

Holmium (Ho)‐doped bismuth ferrite (BiFeO3) nanoparticles are synthesized using the citrate‐gel autocombustion method to investigate their structural, dielectric, ferroelectric, and magnetic properties. X‐Ray diffraction analysis confirms the formation of a rhombohedral perovskite structure, with crystalline size decreasing from ≈14 to 7 nm as doping levels increase. Fourier‐transform infrared spectroscopy further validates the perovskite phase, while field emission scanning electron microscopy and energy‐dispersive X‐Ray spectroscopy confirm the nanocrystalline nature and composition of the samples. X‐Ray photoelectron spectroscopy verifies the successful incorporation of Ho3+ ions into the BiFeO3 matrix. The dielectric properties show high permittivity and low dielectric losses, while magnetic hysteresis loops reveal enhanced magnetic properties, including increased saturation magnetization, remanence, coercivity, squareness ratio, Bohr magneton, and magnetocrystalline anisotropy. These findings indicate that Ho‐doped BiFeO3 nanoparticles exhibit significantly improved electric and magnetic performance, positioning them as promising candidates for applications in magnetic storage devices and sensors.

Stability and Spin Waves of Skyrmion Tubes in Curved FeGe Nanowires.

In this work, we investigate the influence of curvature on the dynamic susceptibility in FeGe nanowires, both curved and straight, hosting a skyrmionic tube texture under the action of an external bias field, using micromagnetic simulations. Our results demonstrate that both the resonance frequencies and the number of resonant peaks are highly dependent on the curvature of the system. To further understand the nature of the spin wave modes, we analyze the spatial distributions of the resonant mode amplitudes and phases, describing the differences among resonance modes observed. The ability to control the dynamic properties and frequencies of these nanostructures underscores their potential application in frequency-selective magnetic devices.

Nanostructural Modification of Fe2O3Nanoparticles: Carbon Coating for Enhanced Magnetic Behavior

In this study, the enhancement of magnetic properties in Fe2O3nanoparticles through nanostructural modification via carbon coating is investigated. Fe2O3and carbon‐coated Fe2O3nanoparticles are synthesized using the solvothermal method. Structural, morphological, optical, and magnetic properties are comprehensively analyzed. The results demonstrate a significant reduction in particle size upon carbon coating, effectively mitigating agglomeration. Furthermore, carbon‐coated nanoparticles exhibit substantial enhancement in coercivity, remanence, and saturation magnetization suggesting improved magnetic behavior in comparison to their uncoated counterparts. This enhancement is attributed to the prevention of spin misalignment at the nanoparticle surface by the carbon coating, as well as the formation of distinct magnetic domains due to the reduced particle size. The observed improvements underscore the effectiveness of carbon coating in tailoring the magnetic properties of Fe2O3nanoparticles for applications in magnetic devices and biomedical systems, such as magnetic hyperthermia and drug delivery systems, where precise control over magnetic behavior is crucial.

Investigation of magnetic and electric properties of bismuth ferrite nanoparticles at different temperatures

Multiferroic bismuth ferrite shows a massive interest in its potential application in magnetic and electronic devices however maintaining high purity in bismuth ferrite nanoparticles at different temperatures is a difficult task for researchers. Several samples are prepared with different annealing temperatures and investigated in different atmospheres to recognize magnetic and electrical properties. A xerogel powder of bismuth ferrite is synthesized by the sol-gel route. The powder then anneals at 500, 600, 700, and 800 °C to form a nanostructure. X-ray diffraction analysis confirms that the annealed samples are in rhombohedral structure with R3c space symmetry and show a significant increase in crystal size and reduction in lattice strain with increasing annealing temperature. FESEM reveals the microstructural features of annealed nanoparticles which represent the conversion of spherical to cubic morphology with annealing temperature. Vibrating sample magnetometer investigations were conducted as a function of annealing and surface (300, 200, 80 K) temperatures. Insignificant variations of saturation magnetization are detected with surface temperature, but considerable degradation is observed with increasing annealing temperatures. The band-gap energy of bismuth ferrite nanoparticles annealed at 500, 600, 700, and 800 ºC is measured and significant escalation is observed from 1.93 to 2.06 eV. Electrical property analyses have been investigated as a function of frequency at different surface temperatures of 50, 100, 150, 200, 250, 300, and 350 °C. Remarkable variations are established in the electric and magnetic properties. Bismuth ferrite has been widely investigated due to its promising multifunctional device applications such as memory devices, spintronics, sensors, actuators, and photocatalytic and photovoltaic applications.

Magnetic Monopole-Like Behavior in Superparamagnetic Nanoparticle Coated With Chiral Molecules.

Superparamagnetic iron oxide nanoparticles (SPIONs) have attracted wide attention due to their promising applications in biomedicine, chemical catalysis, and magnetic memory devices. In this work, the force is measured between a single SPION coated with chiral molecules and a ferromagnetic substrate by atomic force microscopy (AFM), with the substrate magnetized either toward or away from the approaching AFM tip. The force between the coated SPION and the magnetic substrate depends on the handedness of the molecules adsorbed on the SPION and on the direction of the magnetization of the substrate. By inserting nm-scale spacing layers between the coated SPION and the magnetic substrate it is shown that the SPION has a short-range magnetic monopole-like magnetic field. A theoretical framework for the nature of this field is provided.

Ab Initio Studies of Mechanical, Dynamical, and Thermodynamic Properties of Fe-Pt Alloys.

The density functional theory (DFT) framework in the generalized gradient approximation (GGA) was employed to study the mechanical, dynamical, and thermodynamic properties of the ordered bimetallic Fe-Pt alloys with stoichiometric structures Fe3Pt, FePt, and FePt3. These alloys exhibit remarkable magnetic properties, high coercivity, excellent chemical stability, high magnetization, and corrosion resistance, making them potential candidates for application in high-density magnetic storage devices, magnetic recording media, and spintronic devices. The calculations of elastic constants showed that all the considered Fe-Pt alloys satisfy the Born necessary conditions for mechanical stability. Calculations on macroscopic elastic moduli showed that Fe-Pt alloys are ductile and characterized by greater resistance to deformation and volume change under external shearing forces. Furthermore, Fe-Pt alloys exhibit significant anisotropy due to variations in elastic constants and deviation of the universal anisotropy index value from zero. The equiatomic FePt showed dynamical stability, while the others showed softening of soft modes along high symmetry lines in the Brillouin zone. Moreover, from the phonon densities of states, we observed that Fe atomic vibrations are dominant at higher frequencies in Fe-rich compositions, while Pt vibrations are prevalent in Pt-rich.

Tailoring magnetic properties of novel (La0.25Nd0.25Sm0.25Gd0.25)1-xHoxMnO3 high-entropy perovskite ceramics by Ho doping

High-entropy perovskite ceramics (HEPCs) with equal atomic ratios have recently emerged as a highly promising class of materials due to their unique magnetic properties. However, the crystal structure, microstructure and magnetic properties of unequal atomic ratios HEPCs have yet to be fully investigated. In this paper, single-phase HEPCs (La0.25Nd0.25Sm0.25Gd0.25)1-xHoxMnO3 ((LNSG)1-xHxMO) have been synthesized using solid-state reactions. The effect of Ho element content (x = 0.25, 0.3, 0.35 and 0.4) on the structure and magnetic properties was systematically investigated. All samples exhibit an orthorhombic perovskite structure with a Pbnm space group and show obvious crystallization characteristics after sintering at 1250 °C for 16 h (LNSG)1-xHxMO HEPCs display a smooth surface texture and distinct grain boundaries, as well as significant hysteresis effects at T = 5 K. The spin-orbit interaction and magnetic anisotropy between Ho and Mn ions increase with the increase of Ho content, which increases the saturation magnetization (Ms) of HEPCs. (LNSG)0.6H0.4MO exhibits the lowest magnetic hysteresis losses among the considered samples, attributed to its highest Ms (50.95 emu/g) and the lowest coercivity Hc (0.6 kOe). These characteristics endow it with a potential application in magnetic storage devices.

Structural, Optical and Humidity Sensing performance of Lanthanum doped CoCr2O4 nano-ceramics for Sensor Applications

In the present study, we have investigated the influence of Lanthanum doping concentration on the structural, microstructural, dielectric, and humidity sensing performance of rare earth Lanthanum cobalt chromite nanoparticles. These nanomaterials were synthesized by the solution combustion method using glucose and urea as fuels. Structural investigations revealed that the synthesized materials are single-phase, highly crystalline, and porous, with spherical agglomerated nanoparticles of crystallite size ranging from 13 nm to 17 nm. Particle size distribution and pore area distribution were plotted using imageJ software. Energy dispersive spectroscopy confirmed the accurate elemental composition of all samples, consistent with the calculated stoichiometry. Optical absorption studies showed a blue shift in the peak as the doping concentration increased, indicating a quantum confinement effect. Dielectric constant and electrical resistivity measurements ensured that the materials are electrically conducting, which is necessary for humidity sensing applications. Humidity sensing measurements demonstrated that the capacitive humidity sensitivity coefficient (SC) and resistive humidity sensitivity coefficient (SR) were highest for the La (0.05) sample. The XPS survey spectra and high-resolution core-level spectra provide a thorough understanding of the elemental composition, oxidation states, and electronic environments in La-doped cobalt chromite nanoparticles. This detailed analysis is critical for tailoring the material's properties for specific applications in catalysis, electronics, and magnetic devices.

Band Structure Calculations, Magnetic Properties and Magnetocaloric Effect of GdCo1.8M0.2 Compounds with M = Fe, Mn, Cu, Al

The magnetic properties, band structure results, and magnetocaloric effect of GdCo1.8M0.2 with M = Fe, Mn, Cu, and Al are reported. The band structure calculations demonstrate that all the samples have a ferrimagnetically ordered ground state, in perfect agreement with the magnetic measurements. Calculated magnetic moments and variation with the alloy composition are strongly influenced by hybridisation mechanisms as sustained by an analysis of the orbital projected local density of states. The XPS measurements reveal no significant shift in the binding energy of the investigated Co core levels with a change in the dopant element. The Co 3s core-level spectra gave us direct evidence of the local magnetic moments on Co sites and an average magnetic moment of 1.3 µB /atom was found, being in good agreement with the theoretical estimation and magnetic measurements. From the Mn 3s core-level spectra, a value of 2.1 µB/Mn was obtained. The symmetric shapes of magnetic entropy changes, the Arrott plots, and the temperature dependence of Landau coefficients clearly indicate a second-order phase transition. The relative cooling power, RCP(S), normalized relative cooling power, RCP(∆S)/∆B, and temperature-averaged entropy change values indicate that these compounds could be promising candidates for applications in magnetic refrigeration devices.

Perpendicular magnetic anisotropy of Cr/CoFeB/MgO modulated by MgO thickness

The dependence of perpendicular magnetic anisotropy (PMA) on the MgO thickness in Cr/CoFeB/MgO/Ta films has been experimentally investigated. A clear PMA is observed in the as-deposited samples with 1.8 nm MgO while no as-deposited PMA is shown in those with 4.0 nm MgO. This may be attributed to the moderate oxidation degree of CoFeB and larger interfacial anisotropy energy density K i to overcome the volume magnetic anisotropy and demagnetization field. On the contrary, samples with 4.0 nm MgO demonstrate PMA only after annealing, which might be due to the oxygen and boron diffusion during the annealing process. These results would provide a method to optimize the design of CoFeB/MgO structures on 3d metals for future applications in perpendicular magnetic devices.

First-Principles investigations into electronic, magnetic, elastic, and optical phenomena in SmCrO3: Towards spintronic and magnetic storage applications

Using a thorough DFT analysis, this work investigates the electronic, magnetic, elastic, and optical phenomena in the cubic and orthorhombic phases of SmCrO3. The study explores the distinct qualities of both phases, such as their electronic features, magnetic behaviors, and elastic responses, using the GGA-PBE and mBJ-GGA-PBE methodologies. The study highlights the potential of SmCrO3 cubic and orthorhombic structures in spintronics and magnetic device applications by confirming their half-metallic nature. A deeper understanding of the electronic structure and magnetic stability of the materials results from the intricate interplay of spin effects and thorough investigation of magnetic interactions.

Ferrimagnetic pseudocapacitive MnFe2O4 electrodes and supercapacitor devices

This investigation is motivated by the surge of interest in materials, combining high spontaneous magnetization and pseudocapacitance at room temperature. Ferrimagnetic MnFe2O4 offers benefits of high magnetization. However, the non-pseudocapacitive behavior, low capacitance and high resistance of MnFe2O4 are limiting factors for its applications in magnetic pseudocapacitive devices. This investigation demonstrates that nearly ideal pseudocapacitive behavior can be achieved for MnFe2O4 electrodes in Na2SO4 electrolyte. High pseudocapacitance is observed in positive and negative potential ranges and two different charging mechanisms are proposed. High capacitance is achieved at a low impedance. The ability to achieve comparable and high areal capacitances in the positive and negative potential ranges facilitates the fabrication of a symmetric pseudocapacitive device, containing ferrimagnetic MnFe2O4 as cathode and anode material for operation in enlarged voltage window of 1.6 V. The symmetric device shows capacitance of 0.92 F cm−2 at a current density of 3 mA cm−2. The individual electrodes and device show good cycling stability. The approach is based on the use of murexide and gallocyanine as redox-active dispersants and charge transfer mediators. The analysis of testing results provides an insight into the influence of chemical structure, charge and redox properties of the dispersants on the capacitive behavior. The ability to fabricate a pseudocapacitive device, containing two ferrimagnetic electrodes is promising for energy storage, water purification and novel applications based on magnetocapacitive effects.

Concurrence of directional Kondo transport and incommensurate magnetic order in the layered material AgCrSe2

In this work, we report on the concurrent emergence of the directional Kondo behavior and incommensurate magnetic ordering in a layered material. We employ temperature- and magnetic field-dependent resistivity measurements, susceptibility measurements, and high resolution wavelength X-ray diffraction spectroscopy to study the electronic properties of AgCrSe2. Impurity Kondo behavior with a characteristic temperature of TK = 32 K is identified through quantitative analysis of the in-plane resistivity, substantiated by magneto-transport measurements. The excellent agreement between our experimental data and the Schlottmann’s scaling theory allows us to determine the impurity spin as S = 3/2. Furthermore, we discuss the origin of the Kondo behavior and its relation to the material’s antiferromagnetic transition. Our study uncovers a rare phenomenon—the equivalence of the Néel temperature and the Kondo temperature—paving the way for further investigations into the intricate interplay between impurity physics and magnetic phenomena in quantum materials, with potential applications in advanced electronic and magnetic devices.

Directional growth of iron oxide nanowires on a vicinal copper surface

Single-crystal magnetic nanostructures with well-defined shapes attract lots of interest due to their potential applications in magnetic and spintronic devices. However, development of methods allowing controlling their mutual crystallographic and geometric orientation constitutes a significant scientific challenge. One of the routes for obtaining such structures is to grow the materials epitaxially on naturally-structured supports, such as vicinal surfaces of single-crystal substrates. Iron oxides are among the most well-known magnetic materials which, depending on the phase, may exhibit ferro/ferri- or antiferromagnetic ordering. We have grown iron oxide nanowires on a Cu(410) single-crystal substrate faceted with molecular oxygen. Scanning tunneling microscopy and low energy electron diffraction revealed that the oxide grows in the [111] direction, along the step edges of the substrate and rotated by ±15° with respect to the [010] direction of copper atomic terraces (so that the the growing elongated structures are orientated parallel to each other). Notably, x-ray photoelectron spectroscopy confirmed that the nanowires represent the ferrimagnetic γ-Fe2O3 (maghemite) iron oxide phase, while micromagnetic simulations indicated that the wires are single-domain, with the easy magnetization axis orientated in-plane and along the long axis of the wire.