Ferromagnetic Materials Research Articles

Optical solitons solution for the perturbed nonlinear Schrödinger’s equation

In this manuscript, the perturbed nonlinear Schrödinger’s equation (PNLSE) is considered, which has many implications in various fields such as ferromagnetic material, nonlinear optics, and optical fibers. The focus of this paper is to obtain soliton solutions of the perturbed nonlinear Schrödinger’s equation by implementing two analytical methods, namely, tanh–coth method and energy balance method. As an outcome, a various soliton solutions like, breather solitary wave, lump type soliton in periodic background, singular type soliton, and periodic soliton solution obtain via Mathematica. Additionally, the 2D, 3D, and contour plots are used to visualize the graphical propagation of the achieved soliton solutions by selecting appropriate parametric values.

A systematic DFT study of the structural, electronic and magnetic properties of 3d transition metal based double perovskites Rb2MCl6 (M = V, Cr, Mn)

Transition-metal-based halide double perovskites constitute a new fascinating playground for investigating the deep relationship between the crystal structure, unique physical properties and their promising applications. Among these halides, Rb2MCl6 are attractive compounds since they show ferromagnetic, half-metallic (HM) and semiconductor natures due to the M-site substitution effect. In this work, we have studied the structural, thermodynamic, magnetic and electronic properties of perovskites Rb2MCl6 (M = V, Cr, Mn). Theoretically, the current investigations have relied heavily on Wien2k computational code, which exploits the density functional theory (DFT) based on generalized gradient approximation (GGA). Herein, we analyzed the effect of M-3d on the core physical properties of Rb2MCl6. We found that all Rb2MCl6 compounds are stable and crystallize in the face-centered cubic (fcc; Fm-3 m) structure. The electronic band structures and density of states indicate that Rb2MCl6 compounds exhibit HM nature for (M = V and Cr), and semiconductor behavior for (M = Mn). The direct band-gap for HM cases is found to be in the spin-down with 2.128 eV (M = V) and 2.111 eV (M = Cr), whereas (M = Mn)-based semiconductor compound shows a band-gap of 1.264 eV in spin-up and 1.701 eV in spin-down. The magnetic properties confirm that perovskites Rb2MCl6 are ferromagnetic (FM) materials with an integer total magnetic moment of 1.0 µB, 2.0 µB and 3.0 µB, respectively, in good agreement with the expected high-spin state of unpaired electrons on the M-3d ions. The above results reveal that the Rb2MCl6 perovskites are reliable inorganic materials and candidates for spintronics and optoelectronics applications.

Reduced energies for thin ferromagnetic films with perpendicular anisotropy

We derive four reduced two-dimensional models that describe, at different spatial scales, the micromagnetics of ultrathin ferromagnetic materials of finite spatial extent featuring perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. Starting with a microscopic model that regularizes the stray field near the material’s lateral edges, we carry out an asymptotic analysis of the energy by means of [Formula: see text]-convergence. Depending on the scaling assumptions on the size of the material domain versus the strength of dipolar interaction, we obtain a hierarchy of the limit energies that exhibit progressively stronger stray field effects of the material edges. These limit energies feature, respectively, a renormalization of the out-of-plane anisotropy, an additional local boundary penalty term forcing out-of-plane alignment of the magnetization at the edge, a pinned magnetization at the edge, and, finally, a pinned magnetization and an additional field-like term that blows up at the edge, as the sample’s lateral size is increased. The pinning of the magnetization at the edge restores the topological protection and enables the existence of magnetic skyrmions in bounded samples.

Preparation, Magnetic and Mechanical Properties of Fe/Ni-Based Amorphous Fibers.

In this study, we successfully fabricated Fe61Zr10Co5Mo7W2B15 and Ni61Nb19.2Ta19.8 amorphous fibers (AFs) using the melt-extraction method. This method ensured a rapid cooling, uniform quality, minimal defects, and superior performance. Magnetic property analysis revealed that the Fe-based AFs exhibited a single-slope magnetization curve characteristic of paramagnetic or diamagnetic materials, while the Ni-based AFs displayed a rectangular curve with low magnetic hysteresis, typical of ferromagnetic materials. The axial saturation magnetization of as-prepared Ni-based AFs is ~1.5 × 10-7 emu/g, with a coercivity of about 85 Oe. The statistical analysis of tensile tests indicated that Ni-based AFs possess a higher fracture threshold of 2440 ± 199 MPa and a reliability of 14.7, demonstrating greater material safety and suitability for high-performance applications. As opposed to Ni-based AFs, Fe-based AFs present a fracture threshold and of 1582 ± 692 MPa and a reliability 4.2. Moreover, under cyclic loading conditions, Ni-based AFs exhibited less residual deformation and superior elastic recovery with a fracture strength of 2800 MPa. These findings highlight the potential of Ni-based AFs for advanced engineering applications, particularly where high strength, durability, and excellent magnetic properties are required, paving the way for their integration into next-generation technologies.

Mechanism of strain-induced magnetic signal change in ferromagnetic materials under weak magnetic environment

Weak magnetic detection based on force-magnetic coupling effect is widely used in nondestructive testing of ferromagnetic materials, but the weak magnetic signals caused by the deformation of ferromagnetic materials under the action of external load show nonlinear changes, and the existing theories can not make a unified conclusion on the mechanism of nonlinear changes of magnetic signals, which limits the further application of weak magnetic detection. In this paper, a microscopic model of ferromagnetic material is established with the strain of the material as the independent variable. Firstly, the reasonableness of the established model is verified by the stress–strain relationship, and the stress concentration phenomenon generated by the change of the microscopic structure of the model is studied in depth by using the XRD diffraction method, so as to put forward the idea of characterizing the macroscopic stress with microscopic dislocations; secondly, the mechanism of the change of the magnetic signals of the ferromagnetic material caused by strain is analyzed by using the atomic magnetic moments and the density of states. The model explains the mechanism of strain-induced magnetic signal change in ferromagnetic materials, and has a guiding role in the further application and promotion of the weak magnetic method.

An energy efficient way for quantitative magnetization switching

Recent advancements in electrically controlled spin devices have been made possible through the use of multiferroic systems comprising ferroelectric (FE) and ferromagnetic (FM) materials. This progress provides a promising avenue for developing energy-efficient devices that allow for electrically controlled magnetization switching. In this study, we fabricated spin orbit torque (SOT) devices using multiferroic composites and examined the angular dependence of SOT effects on localized in-plane strain induced by an out-of-plane electric field applied to the piezoelectric substrate. The induced strain precisely modulates magnetization switching via the SOT effect in multiferroic heterostructures, which also exhibit remarkable capability to modulate strain along different orientations – a feature with great potential for future applications in logic device arrays. To investigate the influence of electric fields on magnetization switching, harmonic Hall measurements, synchrotron-powered x-ray magnetic circular dichroism-photoemission electron microscopy (XMCD-PEEM), x-ray diffraction (XRD), magnetic force microscopy (MFM), and micromagnetic simulation were conducted. The results demonstrate that electric-field-induced strain enables precise control of SOT-induced magnetization switching with significantly reduced energy consumption, making it highly suitable for next-generation spin logic devices.

A new magneto-plastic coupling model for residual stress description in ferromagnetic materials

The paper addresses the topic of residual stress in magnetic behaviour of the ferromagnetic materials. Carbon steel parts are submitted to several stress loads and the magnetic behaviour is collected at several operating points. After stress load, the hysteresis data are measured and illustrate a complex behaviour in hysteresis morphology where a big belly is observed near coercive field and a short neck in maximum induction zone. In order to describe the B-H curves, a modified Arctangent model is proposed. A comparison between experiments and model signals show a very good accuracy.

Strain-tunable magnetic property of ferromagnetic square CoSe monolayer

Two-dimensional (2D) intrinsic ferromagnetic materials with large perpendicular magnetic anisotropy (PMA) and high Curie temperature have attracted extensive attention for their potential applications. However, 2D intrinsic ferromagnets prepared experimentally are still very few and most of them have low PMA and Curie temperature. Here, using first-principles calculations, we investigate the structural stability, electronic and magnetic properties of square CoSe monolayer. The calculations indicate that CoSe monolayer is ferromagnetic metal with high Curie temperature of 251.9 K and PMA of 0.825 meV/unit cell. Additionally, the effect of biaxial strain on the magnetic and electronic properties of CoSe monolayer is explored. The CoSe monolayer has strong ferromagnetism over a biaxial strain range of −5 % to 5 %. Tensile strain can induce a transition from metal to half-metal. The Curie temperature of CoSe monolayer can be enhanced under compressive strain. Tensile strain increases the magnetic anisotropy energy by 92.2 % compared with that of the unstrained system. The robust ferromagnetism as well as the regulated magnetic anisotropy and Curie temperature of CoSe monolayer provide a new direction for the development of spintronics.

Magnetic properties of ferromagnetic nanoparticles of Fe x GeTe2 (x = 3, 5) directly exfoliated and dispersed in pure water

Fe x GeTe2 (x = 3, 5) are two-dimensional ferromagnetic (FM) materials that have gained significant attention from researchers due to their relatively high Curie temperature and tunability. However, the methods for preparing FM nanoparticles (FNPs) and large-area Fe x GeTe2 films are still in the early stages. Here, we studied the magnetic properties of Fe x GeTe2 FNPs exfoliated via wet exfoliation in pure water. The coercive field of Fe3GeTe2 FNPs increases significantly, up to 60 times, while that of Fe5GeTe2 only slightly increases from that of bulk crystals. Further investigation related to the dimension of nanoparticles and the Henkel plot analysis reveals that the variation in their coercive field stems from the material’s thickness-dependent coercive field and the type of term that governs the interaction between single-domain nanoparticles. Our work demonstrates a facile method for preparing FNPs using van der Waals FM materials and tuning their magnetic properties.

Impact of dimensionality on the magnetocaloric effect in two-dimensional magnets

Magnetocaloric materials, which exploit reversible temperature changes induced by magnetic field variations, are promising for advancing energy-efficient cooling technologies. The potential integration of two-dimensional materials into magnetocaloric systems represents an emerging opportunity to enhance the magnetocaloric cooling efficiency. In this study, we use atomistic spin dynamics simulations based on first-principles parameters to systematically evaluate how magnetocaloric properties transition from three-dimensional (3D) to two-dimensional (2D) ferromagnetic materials. We find that 2D features such as reduced Curie temperature, sharper magnetic transition, and higher magnetic susceptibility are beneficial for magnetocaloric applications, while the relatively higher lattice heat capacity in 2D can compromise achievable adiabatic temperature changes. We further propose GdSi2 as a promising 2D magnetocaloric material. Our calculation predicts that GdSi2 exhibits an isothermal entropy change ΔSM of 22.5 J kg−1 K−1 and an adiabatic temperature change ΔTad of 6.2 K, near the hydrogen liquefaction temperature (TC≈25 K). Our analysis offers valuable theoretical insights into the magnetocaloric effect in 2D ferromagnets and demonstrates that 2D ferromagnets hold promise for cooling and thermal management applications in compact and miniaturized nanodevices.

Induced superconducting correlations in a quantum anomalous Hall insulator

Thin films of ferromagnetic topological insulator materials can host the quantum anomalous Hall effect without the need for an external magnetic field. Inducing Cooper pairing in such a material is a promising way to realize topological superconductivity with the associated chiral Majorana edge states. However, finding evidence of the superconducting proximity effect in such a state has remained a considerable challenge due to inherent experimental difficulties. Here we demonstrate crossed Andreev reflection across a narrow superconducting Nb electrode that is in contact with the chiral edge state of a quantum anomalous Hall insulator. In the crossed Andreev reflection process, an electron injected from one terminal is reflected out as a hole at the other terminal to form a Cooper pair in the superconductor. This is a compelling signature of induced superconducting pair correlation in the chiral edge state. The characteristic length of the crossed Andreev reflection process is found to be much longer than the superconducting coherence length in Nb, which suggests that the crossed Andreev reflection is, indeed, mediated by superconductivity induced on the quantum anomalous Hall insulator surface. Our results will invite future studies of topological superconductivity and Majorana physics, as well as for the search for non-abelian zero modes.

Confined magnon dispersion in ferromagnetic and antiferromagnetic thin films in a second quantization approach: The case of Fe and NiO

We present a methodology based on the calculation of the inelastic scattering from magnons via the spin-scattering function in confined geometries such as thin films using a second quantization formalism, for both ferromagnetic and antiferromagnetic materials. The case studies are chosen with an aim to demonstrate the effects of film thickness and crystal orientation on magnon modes, using bcc Fe(100) and NiO with (100) and (111) crystallographic orientations as prototypical systems. Due to the quantization of the quasimomentum, we observe a granularity in the inelastic spectra in the reciprocal space path reflecting the orientation of the thin film. This approach also allows for the capture of softer modes that appear due to the partial interaction of magnetic moments close to the surface in a thin film geometry, in addition to bulk modes. The softer modes are also affected by crystallographic orientation, as illustrated by the different surface-related peaks of the NiO magnon density of states at approximately ∼65meV for (100) and ∼42meV for a (111)-oriented film. Additionally, we explore the role of anisotropy, revealing that anisotropy increases the overall hardness of the magnon modes. The introduction of a surface anisotropy produces a shift of the surface-related magnon DOS peak to higher energies with increased surface anisotropy, and in some cases leads to a surface-confined mode. Published by the American Physical Society 2024

Exchange bias in heterostructures combining magnetic topological insulator MnBi2Te4 and metallic ferromagnet Fe3GeTe2

Introducing magnetism into topological insulators enables exotic phenomena such as quantum anomalous Hall effect. By fabricating van der Waals (vdW) heterostructures using layered magnetic materials, we can not only induce a gap in the non-magnetic topological surface states through magnetic proximity but also further manipulate the magnetic properties of magnetic topological insulators. However, the scarcity of 2D ferromagnetic insulator materials limits the fabrication of such heterostructures. Here, we demonstrate the vdW heterostructure devices comprising metal ferromagnetic Fe3GeTe2 nanoflakes and few-layer antiferromagnetic topological insulator MnBi2Te4 separated by an insulating hexagonal-boron nitride spacer. These devices exhibit significant exchange bias with the exchange bias field of over 100 mT under certain conditions. Our results prove that besides magnetic insulators, metallic magnets can also effectively adjust the magnetic properties of topological insulators, thereby inspiring diverse configurations of the heterostructures between topological insulators and magnetic materials.

Enhanced Ferromagnetism and Tunable Magnetic Anisotropy in a van der Waals Ferromagnet.

2D van der Waals (vdW) magnets have recently emerged as a promising material system for spintronic device innovations due to their intriguing phenomena in the reduced dimension and simple integration of magnetic heterostructures without the restriction of lattice matching. However, it is still challenging to realize Curie temperature far above room temperature and controllable magnetic anisotropy for spintronics application in 2D vdW magnetic materials. In this work, the pressure-tuned dome-like ferromagnetic-paramagnetic phase diagram in an iron-based 2D layered ferromagnet Fe3GaTe2 is reported. Continuously tunable magnetic anisotropy from out-of-plane to in-plane direction is achieved via the application of pressure. Such behavior is attributed to the competition between intralayer and interlayer exchange interactions and enhanced DOS near the Fermi level. The study presents the prominent properties of pressure-engineered 2D ferromagnetic materials, which can be used in the next-generation spintronic devices.

Misalignment tolerance improvement of loosely coupled transformer with ferromagnetic materials via genetic algorithm

AbstractIn wireless power transfer (WPT) systems, misalignment between the primary and secondary coils can decrease the transmission efficiency of the loosely coupled transformer (LCT). Adding ferromagnetic materials or a relay coil is an effective solution for efficiency and misalignment tolerance improvement if extra eddy current loss and hysteresis loss on the ferromagnetic materials or the conduction loss caused by the relay coil is well controlled. The effect of ferrite cores on the transmission efficiency of two‐coil and three‐coil LCTs is analysed from the perspective of loss. By finite element analysis, the dimension of ferrite cores is optimised via the genetic algorithm to improve the efficiency and misalignment tolerance of the LCT. Optimal ferrite core dimension is also verified in a 1‐kW WPT prototype, and experimental results show that, after optimisation, transmission efficiency of the two‐coil LCT can be improved by 2.681% and 8.930% under alignment and the 200‐mm misalignment, and with the proposed control strategy, transmission efficiency of the LCT is always above 94.925% under various misalignment conditions.

A lift-off suppression algorithm to improve the accuracy of ACFM in crack detection of ferromagnetic materials

Ferromagnetic pressurized components are widely used in petroleum, aerospace and nuclear industries, and their safety and stability are the key to the reliable operation of pressure equipment. In the process of crack detection of ferromagnetic materials by ACFM technology, the changes in lift-off distance caused by coating corrosion and irregularity of the surface will greatly affect the extraction of useful detection signals and reduce the detection accuracy. To overcome the drawback, a lift-off suppression algorithm for crack detection of ACFM is proposed. First, a differential strategy is proposed to discover the time-domain lift-off point of intersection (LOI) from the raw detection signals of ACFM for ferromagnetic materials. Then, the corresponding Bx and Bz signals are demodulated based on the amplitude of the LOI. The simulation and experimental results of the surface cracking of ferromagnetic materials by ACFM show that the novel Bx signals obtained according to the proposed method vary in a small range for different lift-off distances. The lift-off invariant property of the LOI enables the method to improve the interference of the lift-off effect on the conventional Bx signals and to enhance the detection accuracy of crack depth of ferromagnetic materials. The novel Bz signals perform consistently with the conventional Bz signals, and are virtually unaffected by the changes in lift-off distance.

Construction of a cryogenic dual scanner magnetic force microscope equipped with piezoresistive cantilever

We present a low-temperature magnetic force microscope (MFM) incorporating a piezoresistive cantilever and a dual-range scanner for experiments across a wide temperature range from cryogenic levels to room temperature. The piezoresistor-based MFM eliminates the need for optical readjustment, typically required due to thermal expansion at varying temperatures, thereby providing a more stable and precise measurement environment. The integration of a dual scanner system expands the versatility of scanning operations, enabling accurate sample positioning for detailed exploration of magnetic and superconducting properties under diverse thermal conditions. To demonstrate the capabilities of our MFM, we show detailed imaging of Fe3GaTe2, a van der Waals ferromagnet, and Yb0.7Y0.3CuAs2, a ferromagnetic cluster glass material. These studies demonstrate the potential of our MFM in revealing intricate details of magnetic domain dynamics and contribute to our understanding of materials exhibiting the anomalous Hall effect as well as superconducting phenomena.

A measurement method for magnetic moment and magnetic declination of ferromagnetic samples based on rotating magnetic dipole

Abstract This paper presents a novel measurement method for detecting the magnetic properties of ferromagnetic materials. The proposed method uses a motor to rotate the ferromagnetic sample. At the same time, a triaxial magnetometer reads the magnetic field information, and the motor rotation frequency and the magnetometer sampling rate obtain the rotation angle information. A nonlinear optimization algorithm is applied to calculate the magnetic moment and magnetic declination angle of the sample. The effectiveness of the method is proved by numerical simulation and experimental measurement. Our results indicate that the proposed method offers several advantages, including its ease of deployment, simplicity of operation, high accuracy, and robustness. It provides a feasible solution for laboratory-based magnetic moment measurements and rapidly detecting magnetic moments in industrial settings.

Analytical solutions and soliton behaviors in the space fractional Heisenberg ferromagnetic spin chain equation

This study investigates soliton solutions to the (2 + 1)-dimensional space fractional Heisenberg ferromagnetic spin chain equation incorporating beta fractional derivatives that explain the nonlinear propagation of spin wave in the ferromagnetic material with magnetic interactions including the both classical and semi-classical frameworks. This model has applications in spintronics, plasma physics, magnet theory, and condensed matter physics. Employing the two-potential extended Kudryashov and (G′/G, 1/G)-expansion methods, we derive some original and generic solutions composed of trigonometric functions, hyperbolic functions, and their rational forms. For particular values of the parameters, these solutions offer V-shaped, bell-shaped, kink, periodic, flat kink, and singular periodic solitons. The physical behavior of these solitons is demonstrated through three-dimensional, contour, and two-dimensional plots. The results are important in the study of phase transitions in ferromagnetic materials, lattice vibrations in condensed matter, and the propagation of shock waves in plasma. This study also demonstrates the potential and reliability of the employed strategies.

Magneto acoustic emission technique: A review of methodology, applications, and future prospects in non-destructive testing

The magneto acoustic emission (MAE) technique is an emerging non-destructive testing (NDT) method that has shown potential for defect detection in the bulk of material, proven vital for the safety and integrity of the material. The MAE technique has shown promising results among modern non-destructive testing techniques for ferromagnetic materials. Although MAE technique is a long-established NDT method, it has the potential for further development. This paper provides an in-depth review of MAE signals' physical origin and characteristics, compares them with their counterpart, Magneto Barkhausen Noise (MBN), and explores data acquisition methods and applications, including specific case studies in material defect detection. The research gaps in the MAE technique are discussed, and the paper explores potential developments, highlighting future perspectives and possible improvements.