Search

In this paper, we report a systematic study on effect of film thickness and substrate temperature on structural and magnetic behaviour of Fe-Ga films with Cu buffer layer, deposited on Si and Si/SiO2 substrates at room and high substrate temperatures. Grazing incidence X-ray diffraction studies reveal that all the films are crystalline with disordered alpha-Fe phase, which is BCC A2 phase. At 300 °C of substrate temperature, films deposited on Si/SiO2 substrate found to nucleate L12 phase from matrix of A2 phase, which is not seen in Si based films. Irrespective of substrate material, Fe-Ga films found to exist in dual phases at 500 °C substrate temperature. Lattice strains of the films were calculated from X-ray diffraction patterns, using Williamson-Hall method. From X- ray reflectivity analysis of all the films, film density, thickness and roughness of Fe-Ga layer and buffer layer were obtained after fitting the reflectivity data. Presence of an oxide layer is also evident from reflectivity fitting analysis. From magnetization studies it is clear that, all the films exhibited strong in-plane anisotropy. Saturation magnetization of films was found to vary with change in film density and oxide layer thickness of films. Saturation magnetization of films deposited on Si substrates found to decrease with decrease in film density. Coercivity of films found to vary with change in crystallite size, interface roughness and lattice strain of films. Films deposited on Si substrates are sensitive to strain with change in film thickness and films deposited on Si/SiO2 substrates are sensitive to strain with change in deposition temperature. Coercivity in films found to decrease with decrease in film roughness, increase in crystallite size and lowering the tensile lattice strain. [ABSTRACT FROM AUTHOR]

Copyright of Erzincan University Journal of Science & Technology is the property of Erzincan Binali Yildirim Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of La-Co co-substitution on the structural and magnetic properties of strontium M-type hexaferrites (SrM) were carefully investigated for the Sr1−xLaxFe12−xCoxO19 (0.0 ≤ x ≤ 0.3) polycrystalline samples prepared by solid-state reaction in air. Without the use of sintering additives, La-Co co-substituted SrM single phases could be obtained from polycrystalline bulk samples by employing proper processing conditions. The lattice parameter a initially increases with increasing x from 0.0 to 0.1 but gradually decreases with increasing x to 0.20, and then remains almost unaltered up to x = 0.3; the lattice parameter c monotonously decreases with increasing x from 0.0 to 0.25, but it turns to an increase when x = 0.3. The reduction in c/a ratios and Vcell values with increasing x up to x = 0.25 are obviously attributable to the decreasing size effect resulting from La3+ substitution at the Sr2+ site, which surpasses the increasing size effect due to Co2+ and Fe2+ occupancy at the Fe3+ site. Meanwhile, with increasing x from 0.0 to 0.3, while the saturation magnetization (MS) continuously decreases from 75.90 to 72.07 emu/g, the magnetic anisotropy field (Ha) increases from 20.1 to 24.7 kOe, leading to an increase in the intrinsic coercivity (Hci) from 2.68 to 3.99 kOe. The gradual increase in Ha with x, probably caused by a gradual decrease in the crystallographic symmetry, is inversely proportional to the variation in the c/a ratios up to x = 0.25 as usual except when x = 0.3, of which deviation needs further study. [ABSTRACT FROM AUTHOR]

The anhysteretic material magnetization consists in the fact that, simultaneously with a constant magnetizing field having intensity H, an alternating magnetic field is applied to the material, bringing the material to the state of technical saturation, after which the amplitude of the alternating field strength is smoothly reduced to zero. In this case, instead of the initial magnetization curve, one obtains an anhysteretic magnetization curve that is steeper in the case of weak fields and has no inflection point. The use of anhysteretic magnetization is important for attaining an abrupt increase in the sensitivity of different magnetic elements. To simplify the determination of the anhysteretic magnetization curve for a ferromagnetic material, a relationship based on the measurement results for the material magnetization under the conditions of technical saturation, remanent magnetization, and coercive force is developed and substantiated in this paper. An increase in productivity and simplification of determining the anhysteretic material magnetization curve have been achieved owing to the fact that, to determine such a curve, it is necessary to magnetize the material to a technical saturation level only once and, then, to measure the only three magnetic parameters of the saturation hysteresis loop of the material, which can be measured using standard methods with a minimal relative error compared with other magnetic parameters of the material. [ABSTRACT FROM AUTHOR]

The saturation magnetization ( M s ) of a superparamagnetic (SPM) nanoparticle system is an important factor that affects the performance of nanoparticles and can reflect their other physical properties. In this work, we make a comparison between two functions that can be used to extrapolate the room temperature curve of magnetization versus the inverse magnetic field ( M - 1 / H curve) to get saturation magnetization. The functions are the common linear function and the Mittag-Leffler function. Simulated M - 1 / H curves of various systems of SPM nanoparticles were fitted to the functions, and extrapolated M s was obtained. For each fitting procedure, the average absolute deviations (AADs) were calculated. The systems include core-shell iron-oxide nanoparticles with mono-disperse, multi-disperse, log-normal, and bi-log-normal size distributions. The used magnetization fields were up to 20 kOe. The results showed that for each function and each system, the extrapolated M s depends on the number of points of the M - 1 / H curve used in the fitting procedure. However, there are characteristic marks on the diagrams of M s and AAD versus the number of points from which the correct value of M s can be determined. Moreover, for mono-disperse systems with 3nm nanoparticles, the linear function leads to a better result for extrapolated M s than the Mittag-Leffler function. However, for log-normal and bi-log-normal with broad size distributions, the results of the Mittag-Leffler function are better. In the other cases, investigated here, both functions lead to similar and reasonable results. Exploration of M s was also performed for eight samples of iron-oxide nanoparticles that were synthesized by the co-precipitation method. The obtained results from the two functions were compared. The correct value of M s for each sample was determined according to the characteristic mark on the M s and AAD curves versus the number of points. According to the results of this work, we suggest using both functions together to determine the saturation magnetization of magnetic nanoparticles in practical cases. [ABSTRACT FROM AUTHOR]

We synthesized Sr 1- x Nd x Fe 12- y Co y O 19 (x = 0–0.25, y = 0–0.1) using a conventional ceramic route. The crystal structures were analyzed using X-ray diffraction. With increasing Nd3+ and Co2+ contents, lattice constant a increases, while lattice constant c decreases. In terms of magnetic properties, the saturation magnetization and coercivity are simultaneously increased when x = y = 0.1 (equal co-substitution). This is mainly because the bivalent Co2+ has a smaller magnetic moment and unquenched orbital moments. When substitution amount x is further increased (unequal co-substitution), the magnetic properties are further improved and reach the optimum values of M s = 76.4 emu/g and H c = 5115 Oe owing to the occupation of the 2 a site by divalent Fe2+. The occupancies of Co2+ and Fe2+ are further verified using Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Recent years have seen greater interest in manipulating vortex states in magnetic nanostructures for non-volatile memory and logic networks. We show how reducing saturation magnetization locally in ferromagnetic thick nanodot vortex-based spin-torque nano-oscillators modulates their frequency using micromagnetic simulations. When a spin-polarized current and a static in-plane magnetic field are applied to the vortex core of an isolated thick nanodot, the uniform gyrotropic modes and the first higher-order gyrotropic mode resonate at different frequencies in various saturation magnetization areas. The intensity of the first higher-order mode gets almost suppressed in areas with modified saturation magnetization. With linewidths ranging from 25 to 70 MHz with the considered dimensions, these small spin-torque vortex-oscillator devices made of thick Permalloy nanodots seem promising for use in gigahertz signal processing. Our study suggests that locally modifying saturation magnetization may be a cost-effective technique to build dense oscillator and array networks for neuromorphic computing without lithographical fabrication stages. [ABSTRACT FROM AUTHOR]

In this article, boundary conditions for Landau–Lifshitz equations at the interface between two ferromagnets with different interfacial Dzyaloshinskii–Moriya interactions (iDMIs) are derived. We calculated and verified the analytical expression for the energy flux density continuity for the spin-wave (SW) propagation through the ferromagnet with stepwise iDMI considering the boundary conditions mentioned. Analytical expressions for reflection, transmission coefficients, and the nonreciprocity factor are calculated in the case of SW propagation through a ferromagnet with the stepwise iDMI. Two different types of nonreciprocity effects for SW propagation through a ferromagnet with the stepwise interface Dzyaloshinskii–Moriya interaction are revealed for opposite orientations of Dzyaloshinskii–Moriya vector. The material parameters of a ferromagnet and the stepwise iDMIs are found for which the extremely high nonreciprocity factor (>10) is expected according to the results of calculations. The results of this article deepen the knowledge about the SW propagation control in magnonic devices. [ABSTRACT FROM AUTHOR]

A series of charge-balanced Si4+-M1+,2+ (M = Mg2+, K+, Li+) substitution compositions with the chemical formulae of SrFe12−2xSixMgxO19 (x = 0, 0.05, 0.1, 0.2), Sr1−yFe12−ySiyKyO19 (y = 0.05, 0.1, 0.2), and SrFe12−z(Si0.6Li0.6)zO19 (z = 0.05, 0.1, 0.2, 0.4, 0.6) were prepared using conventional ceramic processes. While the sole doping of Si with x = 0.1 (SrFe12−xSixO19 (x = 0.1)) causes a noticeable Fe2O3 phase formation, the co-doping of Si-Mg and Si-Li allow a single M-type phase formation with x up to x = 0.1 and z = 0.4, respectively. Notably, a 2.6% increase in the saturation magnetization was obtained for Si-Li-substituted SrM with z = 0.05—that is, SrFe11.95Si0.03Li0.03O19. Enhancement of the magnet performance can also be achieved when anisotropic permanent magnets are fabricated based on the substitution composition SrFe11.95Si0.03Li0.03O19. The remnant magnetic flux density was improved by 2.5% compared to that of the unsubstituted SrM (from 4207 to 4314 G). The maximum energy product (BHmax) value also increased from 4.24 to 4.46 M·G·Oe. The enhancement in permanent magnet performance is attributed to the increase in the MS of SrM by the optimal Si-Li substitution. This is a promising result because enhanced permanent magnet performance is achieved with intrinsic magnetic property improvement. [ABSTRACT FROM AUTHOR]

The statistical theory of magnetic losses provides a simple and general method for the interpretation and prediction of losses in various magnetic materials. However, there are difficulties in assessing the losses since it would require additional experimental data and is seldom available to device designers. In this article, based on the modified dynamic Jiles–Atherton (JA) model by parameters scaling, a parameter extraction process by three successive steps is proposed for identifying 11 effective parameters applicable to different sinusoidal excitation magnetic fields. It provides a promising solution for the prediction of magnetic losses in giant magnetostrictive material (GMM). First, a quasi-static saturation $B$ – $H$ curve is used to obtain five saturation parameters. Four optimization coefficients are then determined using the arbitrary quasi-static minor $B$ – $H$ curve. Finally, on the basis of the nine parameters determined in the former two steps, two dynamic factors are determined using an arbitrary dynamic minor $B$ – $H$ curve. Then, all 11 coefficients were obtained, which could be used to reliably simulate the hysteresis loop of GMM under different sinusoidal excitation magnetic fields and realize the prediction of magnetic loss. The simulation results of the proposed model are in good agreement with the experimental results, which confirm its validity and accuracy. The proposed parameter extraction process can remarkably reduce the required experiment tests, and only three sets of experimental curves are needed to achieve a fast and accurate prediction of GMM magnetic losses. [ABSTRACT FROM AUTHOR]

FeCo thin films with high saturation magnetization (4 πMs) can be applied in high-frequency electronic devices such as thin film inductors and microwave noise suppressors. However, due to its large magnetocrystalline anisotropy constant and magnetostrictive coefficient of FeCo, the coercivity (Hc) of FeCo films is generally high, which is detrimental to the soft magnetic properties. Meanwhile, the thickness and deposition temperature have significant effects on the coercivity and saturation magnetization of FeCo films. In this paper, FeCo thin films with different thicknesses were prepared by magnetron sputtering at different temperatures. The effects of thickness and deposition temperature on the microstructure and magnetic properties of FeCo thin films were systematically studied. When the film thickness increases from 50 nm to 800 nm, the coercivity would decrease from 309 Oe to 160 Oe. However, the saturation magnetization decreases from 22.1 kG to 15.3 kG. After that, we try to further increase the deposition temperature from room temperature (RT) to 475 °C. It is intriguing to find that the coercivity greatly decreased from 160 Oe to 3 Oe (decreased by 98%), and the saturation magnetization increased from 15.3 kG to 23.5 kG (increased by 53%) for the film with thickness of 800 nm. For the film with thickness of 50 nm, the coercivity also greatly decreased from 309 Oe to 10 Oe (decreased by 96%), but the saturation magnetization did not change significantly. It is contributed to the increase of deposition temperature, which will lead to the increase of grain size and the decrease of the number of grain boundaries. And the coercivity decreases as the number of grain boundaries decreases. Meanwhile, for the thicker films, when increasing the deposition temperature the thermal stress increases, which changes the appearance of (200) texture, and the saturation magnetization increases. Whereas, it has a negligible effect on the orientation of thin films with small thickness (50 nm). This indicates that high-temperature deposition is beneficial to the soft magnetic properties of FeCo thin films, particularly for the films with larger thickness. This FeCo thin film with high saturation magnetization and low coercivity could be an ideal candidate for high-frequency electronic devices. [ABSTRACT FROM AUTHOR]

Magnetically controlled reactors (MCRs) are widely used as reactive power compensation equipment owing to their favorable properties of smoothly adjusting their inductance value through dc bias. However, the dc bias and the rotational magnetization at corner and T-joint areas make the cores of MCRs saturated, resulting in high magnetostriction and vibration. Thus, the electromagnetic vibration analysis of MCRs must consider the vector hysteretic magnetostriction effect. In this article, a vector hysteretic magnetostriction model of silicon steel is proposed by combining the quadratic domain rotation model with the vector inverse Jiles–Atherton model firstly. Then, based on the measured magnetization and magnetostrictive characteristics curves of silicon steel, the model’s parameters are optimized by velocity controllable particle swarm optimization (VCPSO). Finally, the vector hysteretic magnetostriction model is combined with the finite element method (FEM) to simulate the vector vibration characteristics of MCR under dc bias. The simulation results show that the vector property of electromagnetic vibration and magnetic field at the T-joint area is higher than that at other areas. And the MCR vibration test results are consistent with the simulation results, which verify the accuracy of the proposed model in simulating electromagnetic vibration. [ABSTRACT FROM AUTHOR]

The magnetic field-dependent remanent magnetization and demagnetization of magnetite nanoparticles dispersed in a frozen isoparaffin oil have been measured as a function of magnetite concentration. Frozen ferrofluid samples with magnetite volume fractions between 7.1% and 0.03% were demagnetized using either thermal or dc demagnetization and were kept frozen at 77 or 4 K during measurement to restrict mechanical rotation and translation of the particles. The magnetization and demagnetization remanences of the frozen ferrofluid were measured and plotted parametrically in the magnetic field magnitude to produce Henkel and $\Delta M$ plots for comparison with the Wohlfarth model. The Henkel and $\mathrm {\Delta }M$ plots of the ferrofluid samples with higher concentrations of magnetite deviated from the predictions of the Wohlfarth non-interacting model, consistent with demagnetizing interactions in the system. The magnitude of this deviation decreased with decreasing magnetite concentration. A simple model is presented that quantitatively explains the deviations from the expected relations and can be used in other systems to characterize magnetic interactions. [ABSTRACT FROM AUTHOR]

The effect of nanoparticles (NPs) on microwave magnetoresistance in MgO/CoFeB(free)/Ta/CoFeB(fixed)/MgO)/Ta platform and the effect of individual NP on free CoFeB ferromagnetic layer magnetization have experimentally been revealed and analyzed. The area of the platform where magnetization is inverted under scattering field of NPs has been observed. Micromagnetic modeling of dipole magnetic interaction confirms the existence of such areas in “NP-platform” system. The increase in critical field of the platform and the change of resistance under scattering field on NPs have experimentally been revealed. [ABSTRACT FROM AUTHOR]

The dependence of double magnet master (DMM) printing characteristics on master thickness and non-magnetic separator (NMS) thickness is investigated using micromagnetic simulation. It is found that the recording field difference saturates when the master thickness reaches the bit length. The NMS, which separates the two magnetic materials of the DMM, shifts the maximum points of the recording field distribution into the softer magnet regions, decreasing the island-like non-reversed regions, thus enhancing the printing performance. The effective switching field is important for understanding magnetic printing characteristics. The printed magnetization distributions are in accordance with the switching field distribution of the recording field generated by the DMM. Therefore, optimizing the master thickness and NMS thickness effectively improves the DMM printing characteristics for various servo patterns. [ABSTRACT FROM AUTHOR]

We experimentally study a strain-meditated converse magnetoelectric (CME) effect in multiferroic heterostructures consisting of Co2MnSi and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT). To investigate the CME effect, Co2MnSi films are grown on PMN-PT(001) at various growth temperatures by molecular beam epitaxy. Using magneto-optical Kerr-effect and strain measurements, we find that the remanent magnetization state only for the $L 2_{1}$ -ordered Co2MnSi/PMN-PT is modulated by the application of the lattice strain, while that for the $B2$ -ordered Co2MnSi/PMN-PT is insensitive to the strain. We conclude that the formation of $L 2_{1}$ -ordered structure is needed to obtain an effective CME effect in the Co2MnSi/PMN-PT multiferroic heterostructure. [ABSTRACT FROM AUTHOR]

This article presents a novel slot permanent-magnet-assisted hybrid-magnet memory machine (SPMA-HMMM) with hybrid permanent magnets (PMs) in both stator yoke and slot opening. The key is each pair of yoke PMs is composed of one pole of high coercive force (HCF) PM and one pole of low coercive force (LCF) PM with flexible flux regulation. LCF PMs can be freely magnetized and demagnetized through dc current pulses, which are supplied by dc excitation coils wound on LCF PMs. This design leads to high efficiency of machine due to negligible field excitation loss. In this article, the machine configuration and operation principle are illustrated in detail. An equivalent magnetic circuit is modeled to unveil flux regulation and parallel excitation effect. Then, the electromagnetic performances of SPMA-HMMM under different magnetization states (MSs) are investigated, which verify flux regulation ability of the proposed machine with changeable MSs of LCF yoke PMs. [ABSTRACT FROM AUTHOR]

Variable flux memory machines (VFMMs) can have their level of magnet flux density modified by the injection of $d$ -axis current pulses in the armature windings. The use of Fe-Cr-Co magnets as a source of the magnetic field in these machines is still little explored, even if these magnets present interesting thermal and mechanical properties. In this context, this article explores the validation of a standstill magnetization strategy applied in a non-salient single pole pair Fe-Cr-Co-based VFMM designed for high-speed applications in the transportation electrification field. Due to the absence of a well-defined knee on the second quadrant of the hysteresis loop of the magnet used, the methodology commonly seen in the literature for describing the behavior of the recoil lines defining the working points cannot be directly used. Therefore, by the experimental results obtained from the standstill magnetization of the VFMM studied, a new methodology is developed based on the estimation of the remanence in terms of the excitation field characterizing the internal hysteresis loops of the Fe-Cr-Co. The achieved results are compared with the reference obtained from a HysteresisGraph, which represents a closed and ideal magnetic circuit of measurement. The effects of a stator geometry designed with closed slot wedges in the VFMM and the anisotropy shape are explored for justifying the differences observed. [ABSTRACT FROM AUTHOR]

We have systematically investigated the spin-orbit torque (SOT)-induced effective magnetic field in a structure consisting of a Ta heavy metal layer and an antiferromagnetically coupled Mn1.8Ga1/Co2MnSi (CMS) bilayer around the magnetization compensation point by varying CMS film thickness. The efficiency of SOT generation takes the maximum around the compensation point, and it is approximately six times as large compared with that in the devices with a MnGa single structure. The enhancement of SOT efficiency can be explained mainly by the reduction in saturation magnetic moment around the compensation point. Moreover, a significant enhancement of the effective spin Hall angle was observed around the compensation point because of the inversion of the magnetization configuration before and after the compensation point. [ABSTRACT FROM AUTHOR]

Mn 0.6 Zn 0.4 V x Fe 2-x O 4 (x = 0.00–0.10, in steps of 0.02) are synthesized by the solid-state reaction method with a sintering temperature of 1250 °C. X-ray diffraction of the samples confirms the formation of the spinel structure. The grain size is found to increase in morphological investigation of the surface of the samples. The distribution of cations upon vanadium doping in manganese zinc ferrites has not been widely studied before. This study highlights our attempt to formalize a cation distribution to explain our experimental results. Vanadium ions occupying B-sites in their trivalent form may explain the decreasing trend observed in the cell parameters and saturation magnetization, M S values. To support this, theoretical cell parameters and theoretical magnetic moments have been calculated. • Single-phase spinel ferrites are synthesized with increased grain size. • The decrease of saturation magnetization is explained by the Yafet-Kittel model. • Different cation distributions are discussed based on theoretical calculations and experimental findings. • The reduction of Curie temperature vindicates the proposed cationic distribution. • It is concluded that V3+ occupies octahedral B-sites in the investigated ferrites. [ABSTRACT FROM AUTHOR]

In this paper, a novel asymmetric-permanent- magnet hybrid-magnetic-circuit variable flux memory machine (AH-VFMM) is proposed. The low coercive force (LCF) permanent magnets (PMs) are located on one biased side of the hybrid magnetic circuit branch, forming an AH configuration. Compared to its conventional symmetric-PM hybrid-magnetic-circuit (SH) counterpart, the proposed design benefits from the reduced usage of high coercive force (HCF) rare-earth magnet, alleviating the magnetic saturation to improve the flux regulation (FR) range, while the excellent load demagnetization withstand (LDW) capability can be still maintained. The topology evolution and operating principle of the proposed machine are introduced and described, respectively. Then, based on the combination of the magnetic equivalent circuit (MEC) method and Schwarz-Christoffel (SC) transformation, a hybrid analytical model is established to quantitatively reveal the mechanism of FR range extension, and facilitate the initial design of the machine. The electromagnetic characteristics of the proposed machine under different magnetization states (MSs) are investigated and compared with those of the conventional SH counterpart. Finally, an AH-VFMM prototype is manufactured, and the experimental measurements are carried out to verify the validity of the proposed design. [ABSTRACT FROM AUTHOR]

Physics of the spin wave–electromagnetic (EM) interaction is investigated for RF limiter applications, by looking at the magnetization $M$ and its deviation $\Delta M$ through equations of motion. Exchange effects are examined, and a complete magnetodynamics equation is developed and looked at for both the fundamental- and second-harmonic frequencies. Nonlinear conversion of energy occurs between the first and second harmonics. It is shown here that the usual operating frequencies for RF limiters, in the range of 1.5–15-GHz frequencies, can be lifted up into the much higher frequencies of the 40–60-GHz range by a new formula developed from fundamental spin wave–EM interactions in magnetic material characterized by a magnetization $M$. The treatment is self-contained in which all of the information needed to understand the magnetics aspect for RF applications is provided. [ABSTRACT FROM AUTHOR]

The influence of the initial pH of the solution on ferritization in the Fe2+–Co2+–SO42−–OH− system was investigated. Cobalt ferrite was obtained by a combined method of co-precipitation and treatment with contact low-temperature non-equilibrium plasma. The pH varied in the range of 7–12. The phase composition was determined by X-ray phase analysis. Magnetic properties by vibration magnetometry. The stability of the formed complexes was evaluated by the cyclic voltammograms method. Studies have shown that PNC treatment promotes ferritization. In this case, by varying the initial pH value, you can get products with different technological characteristics. As the initial pH value increases, the oxidation rate decreases. According to X-ray examination, with increasing initial pH of the suspension, the degree of crystallinity of the final product increases, and the magnetic parameters (saturation magnetization, forced force) also increase rapidly. The formation of cobalt ferrite occurs at an initial pH 11–12 [ABSTRACT FROM AUTHOR]

In this study, Co/Pt based perpendicular synthetic antiferromagnetic (p-SAF) structures with Ru interlayers are investigated with regard to their magnetotransport properties. The p-SAF structures are varied in their number of Co/Pt multilayer (ML) stacks and Ru interlayers, and are examined for changes in their magnetoresistive effects. The alignment of magnetization directions of the MLs in the ML/Ru/ML stacks of the p-SAF generates a giant magnetoresistance effect (GMR), while the anisotropic magnetoresistance effect (AMR) at each ML further influences the resistance of the system. The GMR is found to increase linearly with the number of Ru interlayers. To extract contributions from the AMR, a simple model is proposed, which explains the observed transfer curves where both effects are taken into account. For the AMR amplitude, it is observed that longitudinal AMR contributions decrease with increasing numbers of Co layers in the p-SAF, whereas transverse components remain constant. While the highest GMR effects are measured at low temperatures, only longitudinal AMR contributions appear to be significantly affected by the measurement temperature. [ABSTRACT FROM AUTHOR]

The Fe76Ge5Ga6B13 and Fe76Ge5Ga6B9Si4 amorphous ribbons were prepared by using the melt spinning technique, and the effects of Ga, Ge, and Si addition on the magnetic properties of the ribbons have been investigated. It was found that Ga and Ge had a great contribution to raise magnetic moment of Fe for Fe76Ge5Ga6B13 ribbon, in which free electrons transferred from Fe to Ga and Ge. Besides, precipitation of Ga and Ge could raise lattice parameter of α-Fe (Ga, Ge), which increased the exchange interacting strength of Fe atoms and thus the ferromagnetism. Si addition could deteriorate the thermal stability of the amorphous ribbons and decrease saturation magnetization of Fe76Ge5Ga6B9Si4 ribbon by preventing the migration of free electrons from Fe to Ge. Moreover, participation of Si reduced lattice parameter of α-Fe (Ga, Ge, Si), weakening the exchange interacting strength of Fe atoms and thus the ferromagnetism. [ABSTRACT FROM AUTHOR]

We study the magnetization dynamics in La-doped yttrium iron garnet thin film induced by a slot line waveguide with the magnetic field applied perpendicular to the plane. The magnetization dynamics depend significantly on the slot line waveguide dimensions, particularly the number of excitation conditions increases with the enlargement of linewidth and the gap between the lines. Such an increase is not observed when the magnetic field is applied to the film plane. The excitation is caused by the interaction between the local magnetization dynamics around the line and the spin waves coming from the other side of the line. Forward volume magnetostatic spin waves are emitted when the magnetic field is applied perpendicular to the film. Their magnetic field dependence of the wavelength change is very gradual, allowing the satisfaction of the resonance condition to be much easier than the in-plane magnetized film. [ABSTRACT FROM AUTHOR]

The design methodologies for variable-flux machines (VFMs), which can illustrate the relationship between the extra torque–speed range and the machine properties of VFMs, are proposed in this article based on the analytical and graphic methods. The operating principles of the VFMs with different salient ratios are analyzed. The influences of machine properties on torque–speed curves are comprehensively studied. Then, the magnetization-state boundary of the non-salient VFM with $i_{d} = 0$ control method is investigated by the analytical method. The design methodology for selecting suitable magnetization state is deduced. Due to the complexity of the transcendental equations for other type machines and control methods, the per unit system and the graphic method are used to obtain the boundary. The influence of the negative $d$ -axis current limit on the torque–speed curves is investigated. The methodology to remedy the influence is given. The proposed methodologies can fully exploit the machine properties and provide the reference guidance in the initial design stage of the VFMs. [ABSTRACT FROM AUTHOR]

Due to friction between components, significant amount of wasted energy is inevitably generated inside a rotary machine during operation. Such wasted energy is commonly in the form of thermal energy that is transferred to machine components through heat conduction, causing the components to expand in geometry. The amount of change also directly affects the machine’s processing accuracy. The study presented in this article aims to use a magnetic encoder and a magnetoresistive (MR) sensor to build a measurement system that can be directly embedded into a high-speed motor to monitor thermal elongation of the motor’s rotating shaft in axial direction. CoMnP is used as magnetic coating on which novel magnetic polarity patterns are magnetized incrementally along the shaft’s axis by utilizing permanent magnet. The proposed system discussed herein this article is designed to determine proper installation specifications and to examine the assembly tolerance, including the pitch, yaw, row, and flying height errors of the MR in a rotating machine. The results demonstrate that the measurement system senses with a 2 kHz sampling rate can real-time monitor the shaft’s thermal elongation while it rotates with high speed from 1000 to 24 000 r/min. Moreover, compared with a commercial product, the measurement system is found to be feasible to provide accurate the shaft’s thermal elongation values with satisfactory accuracy error. [ABSTRACT FROM AUTHOR]

Variable-flux permanent magnet synchronous machines (PMSMs) are considered as a promising candidate in electric vehicle industry for their ability to operate in a wide speed range with high efficiency by manipulating the magnetization state dynamically. A novel high-efficiency series–parallel-connected hybrid-PM variable-flux PMSM is proposed in this article. The topology and operating principle are introduced. The performances, including magnetization/demagnetization ability, PM stability, and torque ability, are analyzed and compared with other hybrid-PM variable-flux PMSMs. The results show that the proposed machine retains the advantages and overcomes the limitations of the existing structures. The steady-state efficiency-maximizing magnetization state adjustment strategy is proposed and evaluated. The torque-speed range is expanded and the proportion of high-efficiency region increases obviously by using this strategy. The efficiency-maximizing magnetization state adjustment strategy considering magnetization state adjustment loss is proposed and evaluated with the worldwide harmonized light vehicles test cycle (WLTC). The efficiency during the whole driving circle is significantly improved by adopting the proposed strategy. [ABSTRACT FROM AUTHOR]

We numerically demonstrated the spin transfer torque oscillation (STO) in a magnetic orthogonal configuration by introducing a 90° magnetic coupling. In our model, the multilayer consists of a top layer with in-plane magnetic anisotropy, a nonmagnetic spacer, and a bottom layer with perpendicular magnetic anisotropy. The advantage of utilizing the orthogonal configuration is the high efficiency of spin transfer torque but it is difficult to stabilize STO. By introducing 90° magnetic coupling into the trilayer of FePt/spacer/Co90Fe10, or Ni80Fe20 or Ni, a stable STO in an orthogonal configuration was realized. When the top layer was Ni with low levels of saturation magnetization, a small damping constant, and a small anisotropy, it exhibited high frequency and low amplitude. This indicates the possibility of controlling the STO frequency. Moreover, the STO frequency was increased by enhancing the 90° coupling. The combination of the orthogonal magnetization structure and 90° magnetic coupling is an effective approach to obtain a stable spin transfer torque oscillator with high frequency. [ABSTRACT FROM AUTHOR]

The accuracy in the measurement of magnetization curve ($M$ – $H$) for soft magnetic materials is easily influenced by the external static field in the unshielded environment. To eliminate the influence from the environmental field, the measurement system must be placed in a zero-gauss chamber. However, such a device is not widely available and also costly. In this work, the rapid $M$ – $H$ measurement system with a giant magnetoresistance (GMR) sensor serving as the zero-field detector is proposed. The $M$ – $H$ curve is obtained by integrating the voltage in the pickup coil to determine the magnetization of the test sample under a sweeping magnetic field. The effect of the environmental static field is eliminated by using the output of the GMR sensor as the trigger signal to determine the offset field in the measured $M$ – $H$ curve. The experimental results show that the $M$ – $H$ curves for various kinds of soft magnetic samples, e.g., mu-metal wire, can be obtained under the interference of an applied static field. The proposed method helps improve the accuracy of the rapid $M$ – $H$ measurement system in the unshielded environment. [ABSTRACT FROM AUTHOR]

The effect of the interfacial Dzyaloshinskii-Moriya interaction ($i$ -DMI) on the magnetization dynamics induced by strain is described within the framework of micromagnetic simulations, taking into account the magnetoelastic coupling between the spin and strain in multiferroic heterostructures. In this magnetized system, a biaxial in-plane strain acting on the perpendicular magnetization without bias magnetic field is introduced. As the micromagnetic simulation results have shown, the lateral magnetization dynamics and spin wave were excited with the $i$ -DMI-induced intrinsic magnetization tilting along the nanostrip width direction. It is found that the excitation strain field could generate a quantized width mode with odd mode numbers. In addition, our simulation reveals that the excitation field with higher frequency generates two spin wave modes with a different mean free path. Our work, therefore, shows the potential of using a strain with the presence of $i$ -DMI as the perspective for integrating spin wave emitters into future logic or computing devices, hinting at possible technological applications in strain-controlled spintronic systems. [ABSTRACT FROM AUTHOR]

The motion of a domain wall in a magnetic film with an antidot array leads to the formation of a vortex magnetization reversal zone moving along the sample. A description of the magnetization dynamics in the film is obtained by micromagnetic simulations based on the Landau–Lifshitz–Gilbert equation for various film thickness and hole arrangement and size. We show that the magnetization reversal zone either passes through the antidot array or “freezes” on it. Using a special technique for visualizing vortex structures, based on the calculation of topological charges of two types, we establish the relationship between the magnetization dynamics and the types of vortex structures. [ABSTRACT FROM AUTHOR]

The magnetic printing onto energy-assisted magnetic recording (EAMR) media by utilizing double magnet master (DMM) media has been demonstrated. The DMM media is effective for improving printing characteristics by enhancing recording field with two different magnetic patterns that consist of high coercivity and low coercivity magnets. The magnetization distributions and printing performances (PPs) for magnetic printing onto EAMR media were evaluated by the micromagnetic simulation. The DMM can clearly print the L/S and checkerboard patterns onto EAMR media, and the DMM PP was superior to that of the conventional master media. The DMM printing could write the servo-signals onto the EAMR media with the coercivity of up to 30 kOe. The narrower switching distributions of grains in EAMR media enhances the printing characteristics. The potential of magnetic printing with DMM media was revealed for writing the servo-signals onto the EAMR media. [ABSTRACT FROM AUTHOR]

We report on an investigation of the temperature-dependent magnetic properties of magnetorheological elastomers (MREs). These are a class of composites that consist of magnetically permeable particles dispersed in a nonmagnetic polymeric matrix. Under the application of an external magnetic field, a large deformation occurs altering the mechanical properties of these materials. Due to their magnetoelastic coupling response, these materials are finding an increasing interest among the scientific community. These polymer-based composites’ performance depends on many factors, which temperature is one of the biggest influencing factors requiring further investigation. In this work, the magnetic properties of isotropic and anisotropic polyurethane-based MRE with different iron (Fe) particle loading fractions (50%, 60%, 70%, and 80% by weight) were investigated under different temperatures. From the analysis, the magnetization curves of these materials are observed to overlap for different measured temperature values. The variation of various magnetic properties including saturation magnetization and differential susceptibility with temperature was also determined. The results show a ~2.5% decrement in the saturation magnetization for each of the loading fractions, between the lowest (300 K) and the highest (400 K) measured temperature. On the other hand, the initial differential susceptibility exhibits different trends with increasing temperature. Generally, the magnetization response of these materials is seen to be only slightly sensitive to temperature changes. In addition, the magnetization response is observed to be highly dependent on particle loading fractions and particle orientation within the elastomer. [ABSTRACT FROM AUTHOR]

The influence of V substitution for Co on the structural, electronic, magnetic, and mechanical properties of quaternary Heusler alloys Co2-xVxFeSi ($x = 0$ , 0.25, 0.50, 0.75, and 1) has been systematically investigated. The microstructural and the scanning profile using energy-dispersive X-ray analysis suggests the single-phase behavior in all alloys except for $x = 1$. The X-ray diffraction analysis at room temperature reveals the $\text{L}2_{1}$ crystal structure promoting lattice expansion after V substitution. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also obey the Slater–Pauling rule. Very high Curie temperature is also observed. The alloys are mechanically robust. First-principles calculation with the implementation of a Hubbard correction term (U) is observed to predict half-metallic behavior. [ABSTRACT FROM AUTHOR]

The first-order reversal curve (FORC) method is one of the most appealing magnetic characterization methods that has been used over decades for detailed analyses of nanoscaled magnetic systems. These detailed analyses are accompanied by numerous magnetic features in FORC diagrams that usually are difficult to explain fully. Here, the FORC diagrams of several magnetic nanowire (MNW) arrays are modeled and discussed. The focus is on how the MNW arrangement (i.e., hexagonal, random, and square) and imperfections (i.e., variation of coercivity, $H_{c}$) effects interaction fields ($H_{u}$) between MNWs, as well as switching events and FORC diagram features. $H_{u}$ in hexagonal arrangements is higher than those in square or random arrangements because hexagonal is a close-packed arrangement, so there are more nearest neighbors. Furthermore, the FORC diagrams features were dictated not only by the $H_{u}$ and $H_{c}$ values but also by their standard deviation ratios ($\sigma _{u}/\sigma _{c})$ , where “Wish-bone” features were observed for $\sigma _{u}/\sigma _{c} \le 1$ and “T-shape” features were observed for $\sigma _{u}/\sigma _{c} \ge 5$. [ABSTRACT FROM AUTHOR]

We report on an experimental study on an observed asymmetry in the magnetization of a sputtered polycrystalline Co–Fe/Ir–Mn exchange bias system. Such asymmetries have been predicted by numerical modeling but have never been measured in detail. In particular, we observe the magnetization asymmetry to increase with decreasing temperature down to 5.5 K. Given that the bulk of the antiferromagnetic grains is known to be stable below 300 K, this indicates that the asymmetry derives from interface spin effects at the ferromagnetic/antiferromagnetic interface. As the temperature is reduced, a peak in magnetization asymmetry is observed below 10 K. We also observed that when measured at low temperature there is an increase in the hysteresis loop coercivity and the well-known training effect on the loop shift in exchange bias systems. These effects both derive from the ferromagnetic/antiferromagnetic interface. [ABSTRACT FROM AUTHOR]

In this article, we propose an energy-efficient spin wave (SW)-based approximate 4:2 compressor including three- and five-input majority gates. We validate our proposal by means of micromagnetic simulations and assess and compare its performance with state-of-the-art SW 45-nm CMOS and spin-CMOS counterparts. The evaluation results indicate that the proposed compressor consumes 31.5% less energy than its accurate SW-design version. Furthermore, it has the same energy consumption and error rate as a directional coupler (DC)-based approximate compressor, but it exhibits a 3× shorter delay. In addition, it consumes 14% less energy while having a 17% lower average error rate than its approximate 45-nm CMOS counterpart. When compared with other emerging technologies, the proposed compressor outperforms the approximate spin-CMOS-based compressor by three orders of magnitude in terms of energy consumption while providing the same error rate. Finally, the proposed compressor requires the smallest chip real estate measured in terms of devices. [ABSTRACT FROM AUTHOR]

This work aimed to tune the comprehensive properties of Fe-P-C-based amorphous system through investigating the role of microalloying process on the crystallization behavior, glass forming ability (GFA), soft magnetic features, and mechanical properties. Considering minor addition of elements into the system, it was found that the simultaneous microalloying of Ni and Co leads to the highest GFA, which was due to the optimization of compositional heterogeneity and creation of near-eutectic composition. Moreover, the FeCoNiCuPC amorphous alloy exhibited the best anelastic/viscoplastic behavior under the nanoindentation test, which was owing to the intensified structural fluctuations in the system. However, the improved plasticity by the extra Cu addition comes at the expense of magnetic properties, so that the saturation magnetization of this alloying system is significantly decreased compared to the FeCoPC amorphous alloy with the highest soft magnetic properties. In total, the results indicated that a combination of added elemental constitutes, i.e., Fe69Co5Ni5Cu1P13C7 composition, provides an optimized state for the comprehensive properties in the alloying system. [ABSTRACT FROM AUTHOR]

The gyromagnetic nonlinear transmission line (NLTL) is a promising compact, solid-state, and frequency-agile high-power microwave (HPM) source. This article discusses the minimum spatial filling rate of the ferrite required to excite the microwave oscillations in the gyromagnetic NLTL based on simultaneously solving Maxwell’s equation and Landau–Lifshitz–Gilbert (LLG) equation in the 2-D cylindrical coordinate system. The results reveal that the different filling rate of the ferrite affects the output waveforms. When the filling rate of the ferrite is lower than 50%, the gyromagnetic NLTL is not able to excite significant oscillations. With the increase of the filling rate, the oscillations become more and more violent. Moreover, the influences of the inner radius of the outer conductor and the dielectric materials are also studied in this article. It is found that with the inner radius of the outer conductor increasing, the oscillations are reduced. The dielectric materials have no significant effects on the performance of the gyromagnetic NLTL when the gyromagnetic NLTL is long enough. This kind of characteristic is important for engineering design. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)