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A giant magnetoresistance (GMR) sensor with a Wheatstone bridge structure and an out-of-plane linear response was developed. The spin-valve structure consists of a synthetic antiferromagnetic [(Co/Pt)n/Ru/(Pt/Co)n] reference layer with perpendicular magnetic anisotropy, a Cu spacer layer, and a Co-free layer with in-plane easy magnetization. By utilizing the spin–orbit torque induced magnetization switching in the synthetic antiferromagnetic layer, the magnetization of the reference layers in the adjacent bridge arms is set to the opposite direction, achieving a GMR sensor with a full Wheatstone bridge structure. The sensor exhibits linear response to the out-of-plane magnetic field with adjustable dynamic ranges from hundreds to thousands of Oe, depending on the thickness of the Co-free layer. A similar Wheatstone bridge sensor consisting of magnetic tunnel junctions was also proposed. The sensor with out-of-plane linear response may have promising applications in three-dimensional magnetic field detection and current sensing field.

3D Lidar is the key perception module of Unmanned Surface Vehicle (USV). Targets in the background of the water are affected by refracted light. The visual sensor is difficult to detect in special scenes, which affects the autonomous navigation and obstacle avoidance function. This paper proposes a 3D lidar-based VoxelNet detection algorithm for water surface targets. The sparse point cloud data on the water surface is divided into voxel form, and the hash table is input for efficient query, and the feature tensor is extracted through the feature learning layer and input into the convolutional layer to obtain the global target Information to achieve high-precision target detection. Experimental results show that the surface target detection algorithm based on 3D lidar improves 13.6% compared with the visual solution, which provides a more effective technical means for the intelligent process of USV.

In this article, the temperature-dependent complex Hall effect near the magnetization compensation temperature of CoGd alloy films is systematically studied. We find anomalies of Hall loops with characteristics similar to the topological Hall effect (THE), which is usually considered to indicate the occurrence of topological spin texture. However, the THE is ruled out by detailed magnetic and transport measurements on CoGd alloy films with different composition ratios. After considering the influence of the spin-flop effect and the inhomogeneity of the components naturally formed in the ferrimagnetic CoGd alloy, we constructed a phenomenological model that can explain the complex Hall effect near the magnetization compensation point without relying on the THE. The main result is helpful for explaining the microscopic magnetic properties and transport properties of rare-earth transition metal ferrimagnetic alloys near the compensation point.

We have systematically studied the magnetoresistance effect in $\mathrm{Pt}/{(\mathrm{CoNi})}_{n}$ multilayers featured with perpendicular magnetic anisotropy and fcc (111) texture. Angular dependence of the magnetoresistance, including high-order cosine terms, was found in the plane perpendicular to the electrical current, which can be attributed to the geometrical size effects and the anisotropic interface magnetoresistance effect. However, the contribution from spin Hall magnetoresistance (SMR) is absent. The spin Hall angle of Pt was evaluated by spin-torque ferromagnetic resonance measurements, and the theoretical magnitude of SMR in our samples was estimated to be one order higher than the accuracy of our experiments. The absence of SMR in our multilayers indicates that the Elliott-Yafet spin relaxation of itinerant electrons in the ferromagnetic metal is crucial when studying the spin transport in all-metallic heterostructures.

With the continuous development of intelligent assembly industry, the research on robotic assembly systems has became a hot and cutting-edge issue concerned by powers. During the development of the system, robot vision is mainly used for tracking and positioning. In the establishment of robot vision system, image preprocessing technology is one of the key steps. This paper is aiming at the robot system assembled on the ground of the satellite, which involves machine vision part, the median filtering method and mean filtering method are analyzed through PSNR of peak noise ratio and fuzzy coefficient based on Matlab platform. The noise reduction ability of the five filtering algorithms, including gaussian filtering, guided filtering and bilateral filtering. Then, comparing the best algorithm with the operation time, bilateral filtering has the best effect on image noise reduction and the longest time.

In this study, we systematically investigate the temperature dependence of effective damping in FeNi (permalloy or Py)/Gd bilayer based on broadband ferromagnetic resonance. Despite a significant increase in the effective damping of the Py/Gd bilayer with decreasing temperature, we show that the spin pumping is not responsible for the result. By combining our findings with systematic measurement data of Py/Cu/Gd contrast samples, we conclude that an effective damping enhancement from a decrease in temperature is due to the temperature-dependent magnetic moment of Gd and antiferromagnetic coupling between Py and Gd. Further, we perform a semiquantitative analysis of the experimental data using the Landau-Lifshitz-Gilbert equations that consider the antiferromagnetic coupling between Py and Gd, and estimated the damping parameters in the range of 0.3--0.4 for Gd films with thicknesses of 5 and 8 nm. Our results suggest that to analyze the spin transport in heterostructure with several magnetic layers, it is necessary to commence from the fundamentals of magnetization dynamics considering interlayer coupling and avoid the overuse of spin pumping.

The exact measurement of spin-orbit torque (SOT) in magnetic heterostructures is the basis for a solid understanding of its physical mechanism. Although different SOT terms can be properly separated from harmonic Hall voltage analysis, owing to different symmetries and magnetic-field dependences, this method may be invalid for a ferromagnetic layer with a small Hall coefficient. Here, we develop a method to determine the SOT from harmonic longitudinal voltage measurements. Starting from a standard total-energy expression of a magnetic system, the equations to compute the corresponding SOT effective fields are derived and then applied to an in-plane magnetized $\mathrm{Pt}/\mathrm{Ni}\text{\ensuremath{-}}\mathrm{Fe}/\mathrm{Mg}\mathrm{O}$ system. The effective SOT fields and spin Hall angle obtained for the system are in accordance with previous results measured by other methods. Our results illustrate the applicability of harmonic longitudinal voltage measurements for studying current-induced torques in magnetic heterostructures.

Current-induced spin–orbit torque (SOT) allows for highly efficient control of magnetization for the magnetic memory and the logic application, but its high critical current density Jc limits its applications. Here, we report that the surface acoustic wave (SAW) presents a promising approach for reducing Jc in Pt/Co/Ta heterostructures with perpendicular anisotropy. By the second harmonic Hall measurements, we find that the damping-like SOT effective field is almost the same with or without SAW, implying that the reduction of Jc does not originate from the enhancement of the SOT. However, the current-induced domain wall velocity v under SAW is greatly enhanced. By fitting with the creep law under SAW, we find that lnv is linear with SAW power (P), which reveals that the effective pinning barrier is reduced linearly with increasing P. This feature can be well described by the time average of the periodically accumulated nucleation probability under SAW. The results shed light on the application of SAW-assisted SOT devices for low consumption storage.

Spintronic devices can realize multilevel state storage and mimic the properties of the synapse, which enables their potential application in the field of artificial neural networks. In this paper, we demonstrate the existence of a large intermediate transition zone in current-induced magnetization switching curves of Pt/Co–Tb/Ta structures, and the number of states in the transition zone that can be manipulated by changing the Co content. The magneto-optical Kerr microscope imaging indicates that this property is related to the constrained domain wall motion in the Co–Tb films with large Co content. We also demonstrate the multilevel state storage properties of the sample by applying a sequence of current pulses. The synaptic plasticity behaviors were mimicked in these samples through regulating the value of Hall resistance by current pulses. The constrained domain wall motion supplies a simple but effective way to achieve multilevel state storage and show potential applications in neuromorphic computing.

Magnetic properties and high frequency characteristics of (Fe70.6Co29.4)100−xZrx (x = 4.0 − 18.2 at.%) thin films have been investigated. The saturation magnetization 4πM s decreases continuously from 21.7 kGs for x = 4.0 at.% to 12.2 kGs for x = 18.2 at.% and it is consistent with the decreasing of Fe-Co composition. It is found that the films show nearly isotropic magnetic behavior in the film plane for the Zr content ranging from 7.2 to 18.2 at.%. These films exhibit a weak perpendicular magnetic anisotropy with coercivity values of 24–67 Oe. Meanwhile, the in-plane isotropic FeCoZr films show a good high frequency response of permeability. In particular, the film with x = 7.2 at.% shows a resonance frequency of 2.8 GHz along the direction perpendicular to the stripe domain axis. The permeability spectra of the thin films with higher Zr content display multiple resonance peaks, which may be due to the perpendicular magnetic anisotropy induced by the stress.

In order to ensure flight safety and eliminate hidden dangers, it is very important to detect aircraft track anomalies, which include track deviations and track outliers. Many existing track anomaly detection methods cannot make full use of multidimensional information of the relevant track. Based on this problem, an aircraft track anomaly detection method based on the combination of the Multidimensional Outlier Descriptor (MOD) and the Bi-directional Long-Short Time Memory network (Bi-LSTM) is proposed in this paper. Firstly, track deviation detection is transformed into the track density classification problem, and then a multidimensional outlier descriptor is designed to detect track deviation. Secondly, track outliers detection is transformed into a prediction problem, and then a Bi-LSTM model is designed to detect track outliers. Experimental results based on real aircraft track data indicate that the accuracy of the proposed method is 96% and the recall rate is 97.36%. It can detect both track deviation and track outliers effectively.

We found that the exposure of a Co/Pt bilayer to air will result in a trace amount of oxidation at the Co/Pt interface, while the Pt layer is immune to oxidation. The appearance of CoOx results in a negative spin Hall magnetoresistance and unconventional spin–orbit torques (SOTs), which are observed through temperature-dependent transport and spin-torque ferromagnetic resonance measurements. These results can be understood by considering CoOx as an individual magnetic layer between Pt and Co, with two important characteristics: (1) its magnetization is aligned in the plane that is perpendicular to the magnetization of Co and (2) the spin transparency of CoOx increases with increasing temperature. These results help us understand the features of spin transport at the interface when oxidation occurs and further indicate that trace amounts of oxidation can be a highly effective method to control SOT in magnetic heterostructures.

We systematically investigate the magnetization precession processes of post-prepared and after-annealing Pt buffered [Co/Ni]n multilayers with adjustable perpendicular magnetic anisotropy (PMA) by time-resolved magneto-optical Kerr effect. The PMA of the [Co/Ni]n multilayers could be modulated by changing the number of Co/Ni periods n, Pt thickness tPt and annealing temperature Ta, respectively. With a fixed tPt, both uniaxial magnetic anisotropy Ku and intrinsic damping constant α0 could be modulated by the variation of n. We observed that α0 is linearly proportional to Ku, since both of them originate from the spin–orbit coupling (SOC). For a fixed n, with the increase of tPt, Ku exhibits a non-monotonic change behavior, but α0 increases monotonously. It is found that α0 shows a nonlinear positve correlation to Ku. It suggests that the SOC is not the only factor affecting the damping process. Finally, for the specific sample, both α0 and Ku also display the different variation behaviors with increasing Ta. In this case, the changes in film microstructure caused by the annealing have different contributions to Ku and α0, resulting in a negative correlation between Ku and α0. The findings could be helpful to design the potential application of [Co/Ni]n multilayers system in STT-MRAM with high density, low power and high thermal stability.

Recently, electrical switching of interface states in nonferromagnet/ferromagnet (FM)/antiferromagnet (AFM) heterostructure using spin–orbit torque (SOT) is promising due to its high efficiency, zero magnetic field, and multilevel memory state. However, the reversal mechanism of the AFM interface state is still unclear. In this work, we explained the bipolar current switching of the AFM interface state at zero magnetic field by spin–orbit torque (SOT) in a perpendicularly magnetized Pt/Co/IrMn multilayer. By considering symmetry, we reveal that the mechanism behind the AFM interface bipolar current switching is consistent with FM layers perpendicularly switching induced by SOT. The distinct AFM bipolar current switching by SOT is contributed to the symmetry broken by adjacent FM interface coupling. Under such broken symmetry, the antiparallel interface configuration (AP) between FM and AFM could be switched to parallel configuration (P) for both positive and negative currents; however, P is only allowed to be switched to the AFM multiple domain configuration (M), instead of AP. Our result will be helpful for the formulation of a comprehensive understanding of AFM switching induced by SOT and for the development of the interface AFM spintronic devices.

Although transition metal (TM)-rare earth (RE) alloy film has potential application as an information storage medium in spintronic devices, study of the physical mechanism and microscopic process for the current-induced magnetization switching by spin–orbit torque (SOT) in TM-RE is still inadequate. In this work, we investigated the SOT effect and its driven magnetization switching in Pt/Co–Tb/Ta structures with various Co–Tb compositions. The results show that the current-induced SOT effective fields follow 1/Ms law near the compensation composition in this structure. Because of the large SOT effective field and the low coercivity for the Co–Tb layer near the compensation composition, the current-induced magnetization switching with a threshold current density as low as 1010 A/m2 was achieved in the system. The direct Kerr imaging on the switching process verifies two different current-induced switching mechanisms in the Pt/Co–Tb/Ta system.

We report the direct evidence of the stabilization of magnetic skyrmion bubbles (SkBs) in confined trench and hole structures. By using a high-resolution atomic force microscope, we demonstrated that SkBs exhibit smaller sizes in nanoscale holes and trenches compared with that in uniform films. Our micromagnetic simulations indicate that emergence of the magnetic anisotropic gradient in these confined geometries has an additional contribution to the decrease in SkBs' sizes.

The microscopic mechanism for the current-induced spin–orbit torque (SOT) in magnetic heterostructures is still under debate. The accurate measurement of SOT effective fields and their thickness dependence is the basis for understanding this issue. In this work, we measured the SOT effective fields for Pt/NiFe bilayers by utilizing the harmonic longitudinal voltage (HLV) method with a Wheatstone bridge structure. Benefiting from the elimination of the linear resistance in the bridge structure and the large magnetoresistance difference resulting from the large length–width ratio of the bridge element, we achieved very high measurement accuracy for both field-like and damping-like effective fields in the Pt/NiFe bilayers. On this basis, we demonstrated the possibility of the SOT measurement with a relatively low current density (∼109 A/m2) by utilizing the HLV method with a Wheatstone bridge structure and found that the method we proposed is also applicable to the Pt/CoFeB system with a low anisotropic magnetoresistance ratio.

The spin torque effects discovered in spintronics have a broad prospect for applications in information memory and logic devices, wherein deterministic switching is highly desired. Variations between devices originating from the fabrication process and inherently random physical features are detrimental to memory and logic devices; however, they are potential entropy sources for hardware security primitives. Here, we demonstrate two types of spin–orbit torque (SOT)-based reconfigurable physically unclonable functions (rPUFs) that are based on process-induced SOT switching current variations and SOT-induced domain wall (DW) nonlinear dynamics, respectively. The experimental results show that both rPUFs have excellent performance in terms of reliability and uniqueness, and the performance is sustained after reconfiguring. Furthermore, the DW nonlinear dynamics-based rPUF can be reconfigured for an unlimited number of times with high uniformity. We believe that our work paves a way for information security and expands the application fields of spintronics.

High-frequency studies, of exchange-coupled multilayer films, are the key to advance the development of fast switching spintronic devices. In this paper, we utilize the first-order reversal curve (FORC) to improve the understanding of the spin-reorientation transition process when the permalloy (Py) thickness increases. We also investigate the temperature dependence of the high-frequency properties of exchange-coupled [Co/Pd]6/Py (t nm) multilayer films during the spin-reorientation transition (SRT). The results show that the phase state of the magnetic domain changes, from the perpendicular phase to the multi-domain phase as the Py layer increases during the SRT. The temperature-dependent high frequency results indicate that the resonance linewidth ΔHres increases gradually when the temperature decreases from 300 K to 50 K. Our experimental study offers new insight into the SRT process in exchange-coupled multilayer films and can help to promote the development of fast switching spintronic devices.

In contrast to traditional concepts that eliminate magnetic impurities to achieve larger thermoelectric efficiencies, we report an enhanced thermoelectric efficiency for Cu through doping with the magnetic impurity Co. With doping concentrations from 15% to 30%, the amplitude of the Seebeck coefficient increases from 1.90 μV/K up to 16.3 μV/K, which greatly enhances the thermoelectric efficiency (i.e., power factor). Measuring the magnetoresistance and magnetothermoelectric powers at different temperatures indicates that the enhancement of thermoelectric efficiency is a result of spin-dependent scattering from Co nanoparticles, which are less sensitive to the superparamagnetic transitions. Our finding illustrates a path for the use of nanomagnets to develop potential thermoelectric materials.

Recently, magnetic skyrmion has attracted much attention due to its potential application in racetrack memory and other nanodevices. In bulk chiral magnets with non-centrosymmetric crystal structures, skyrmion lattice phase has been extensively observed. However, in film or multilayers with interfacial Dzyaloshinskii–Moriya interaction, individual skyrmion is often observed. Here, we report a short-ordered skyrmion lattice observed in [Ta(5.0 nm)/CoFeB(1.5 nm)/MgO(1.0 nm)]15 multilayer in a remnant state. The structure, stabilization, and reversal of these skyrmions are discussed. Applying a slightly tilted in-plane magnetic field caused reversal of the skyrmion lattice. This reversal came from disappearance of skyrmions and nucleation of new skyrmions in the interstitial regions of the lattice. Also, we investigated how the skyrmion lattice depended on the CoFeB thickness. Our findings provide a pathway to stabilize and reverse the skyrmions in multilayers films.

Magnetic bubbles are topologically spin textures that offering the interesting physics and great promise for next-generation information storage technologies. The main obstacles so far are that magnetic bubbles are generated with no field stimuli in new material systems at room temperature. Here, we report the observation of individual magnetic bubbles and its high frequency measurement at room temperature in an exchange-coupled [Co/Pd]4/Py multilayers. We demonstrate that the emergence of magnetic bubbles at remanence can be tuned by the in-plane tilted magnetic field (roughly 3{\deg}) along the film plane at room temperature. High frequency results indicate that the presence of magnetic bubbles leads to broadening of the magnetic permeability spectrum lines (due to the non-uniformity of the magnetic moments). Our findings open the door to the bubble-based spintronics at room temperature in exchange-coupled magnetic multilayers., Comment: 15 pages, 7 figures

Domain wall based devices such as racetrack memory have been proposed as promising candidates for high capacity, non-volatile information storage [1, 2]. In these devices, multiple domain walls can be propagated through nanowires at speeds of many hundreds m/s using spin transfer torque, thus allowing data to be written, read and processed. One of the main challenges towards the commercial realization for domain wall memory is the stochasticity of domain wall motion. In thin film systems, where domain wall motion is the dominant reversal mechanism, the magnetization reversal does not happen in a controlled fashion but instead forms zig-zag domains extending over several micrometers in length to form. Such stochastic behavior limits the maximum data density. To overcome this issue, researchers have used lithographically fabricated notches to act as domain wall pinning centers [3]. The other method to form pinning centers is based on exchange bias [4]. In our previous study, we proposed the use of non-magnetic metal diffusion or ions implanted locally to control and pin domains in nanowires [5]. In this report, we demonstrate the formation of pinning centers by using exchange interaction between films with perpendicular magnetic anisotropy and in-plane magnetization to create locally tilted magnetization. The perpendicular magnetic anisotropy (PMA) material Ta (1)/Pt (5)/[Co (0.3)/Ni (0.4)] 3 (0.4)] 3 (all thickness values are in nm) multilayers were deposited on Si (SiO 2 ) substrate and the in-plane magnetic (IMA) anisotropy material Co 10 Ni 90 (2.5 nm) alloy was grown on top of the PMA layer. The thickness of a Pt spacer layer between the PMA layer and IMA layer was varied to tune the angle of magnetization. Figure 1(a) shows film stack studied in this report. The hysteresis loops of films with various Pt spacer layer thickness in the in-plane direction and out-of-plane direction are shown in (b) and (c) respectively. At Pt layer thickness below 2 nm, the switching behavior of the PMA and IMA layer suggests the presence of exchange interaction between the layers. While a thicker Pt layer of 5 nm causes the switching behavior to be independent of each other and thus increasing the coercivity [6]. Mumax3 simulation was performed to study the domain wall pinning effect and depinning current with various tilt angles. Figure 2(a) shows the domain wall propagation without pinning. Figure 2(b) shows domain wall propagation with a pinning center, where the magnetization is tilted at 5 degrees from the perpendicular axis. The result shows that the domain wall is pinned at the edge of the pinning center. Our results further indicate that the magnetization tilt angle can be increased to decrease the barrier energy, which reduces the depinning current as demonstrated in figure 2(c).

In this work, we report the magnetic properties, domain structures and high frequency properties of FeCoAlON alloy films prepared by reactive magnetron sputtering. With increasing N addition content, the films transfer from in-plane anisotropic properties to isotropic behavior. The obvious stripe domain structure is observed in the films with high N content, and the domain parameters depend on the thickness of the films. The XRD analysis indicates that the stripe domain may origin from the stress-induced perpendicular anisotropy by Al, O and N addition. Meanwhile, a double-peak resonance behavior is observed in the permeability spectra of the films with stripe domain structure.

The magnetization reversal induced by spin orbit torques in the presence of Dzyaloshinskii-Moriya interaction (DMI) in perpendicularly magnetized Ta/CoFeB/MgO structures were investigated by using a combination of Anomalous Hall effect measurement and Kerr effect microscopy techniques. By analyzing the in-plane field dependent spin torque efficiency measurements, an effective field value for the DMI of ~300 Oe was obtained, which plays a key role to stabilize Néel walls in the film stack. Kerr imaging reveals that the current-induced reversal under small and medium in-plane field was mediated by domain nucleation at the edge of the Hall bar, followed by asymmetric domain wall (DW) propagation. However, as the in-plane field strength increases, an isotropic DW expansion was observed before reaching complete reversal. Micromagnetic simulations of the DW structure in the CoFeB layer suggest that the DW configuration under the combined effect of the DMI and the external field is responsible for the various DW propagation behaviors. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Published version

We report the annealing effect of CoFeB/MgO/CoFeB magnetic tunnel junctions with a thin free layer. For the junctions with CoFeB free layer below the critical thickness, the MR transfer curves are always hysteresis-free and TMR ratio decreases with increasing annealing temperature. For the junctions with CoFeB free layer above the critical thickness, with increasing annealing temperature, both TMR ratio and coercivity increase firstly and then decrease, and finally hysteresis-free MR transfer curves are obtained. The MR loops without hysteresis can be well fitted by using the Langevin equation, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. This behavior originates from the transformation of the ultra-thin CoFeB free layer during annealing: crystallization process of CoFeB and diffusion at MgO/CoFeB and CoFeB/Ru interfaces.

Laser induced magnetization dynamic behaviors of SmxFe1-x thin films with tunable x (0.25x0.5) are investigated by the time-resolved magneto-optical Kerr effect. It is found that the demagnetization process is accomplished by a two-stage process, the demagnetization time of stage I is within 1.0 ps (t1) for all the samples with different x, while it increases from 0 to 16 ps at stage II (t2) due to the reduced exchange coupling. By introducing an additional magneto-elastic energy contribution, the dispersion relation of precession frequency is deduced, by which the field-dependent frequency curves are well fitted.

The interest in spintronics devices based on domain wall (DW) motion has gained attention for many years. However, the stochastic behaviour of DW motion is still a fundamental issue for the practical implementation of DW devices. In this study, we demonstrate that effective domain wall pinning can be achieved by using exchange interaction between Co/Ni multilayer with perpendicular magnetic anisotropy (PMA) and Co layer with in-plane magnetic anisotropy (IMA) to create locally tilted magnetisation. The strength of exchange interaction is tuned by varying the thickness of spacer layer Pt between the PMA and IMA layers, thus forming different tilt angles. Micromagnetic simulations were performed to verify the relation between pinning field and magnetisation tilt angle. Polar Kerr microscopy shows the current-driven DW pinning and depinning in the Co/Ni multilayer device with Co crossbars, where the thickness of spacer layer Pt is 1 nm. The proposed approach can potentially be used in future DW memory device applications. Accepted version

Interfacial Dzyaloshinskii–Moriya interaction (iDMI) receives a lot of attention due to its potential for spintronics devices. The physical understanding of the artificial approaches that control the strength of iDMI remains complicated. In the Ta/Pt/CoFeB/MgO/Ta system, the strength of the iDMI D and the efficiency of the damping-like spin Hall torque (DL-SHT) have been quantified utilizing Brillouin light scattering, spin-torque ferromagnetic resonance, and spin Hall magnetoresistance. A linear relationship between D and DL-SHT efficiency was obtained, indicating that DL-SHT efficiency governed by itinerant electron spin is a comprehensive parameter for iDMI study.

Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin–orbit coupling in a material can convert a charge current into a pure spin current (a flow of spin momenta without a charge flow) and generate a spin–orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and optical-based measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.

High frequency properties of exchange-coupled multilayers are important to develop future fast switching spintronic devices. Here, we report an experimental investigation of temperature-dependent high frequency properties in [Co/Pd]n/Py multilayer thin films. The results demonstrate that the linewidth varies with the number of cycles at room temperature. However, the damping slightly decreases with increasing repetitions of Co/Pd. By fitting the relationship between the linewidth and the angle (the out-of-plane azimuthal angle of the external magnetic field), we found that a similar two-magnetron scattering effect becomes stronger when the number of Co/Pd cycles increases. For the (Co/Pd)10/NiFe sample, the linewidth became larger at 9 GHz and 16 GHz with the decrease of temperature. Our findings help comprehend the high frequency properties of exchange-coupled multilayer thin films and are useful for fast switching magnetic devices.

In this paper, we report the giant electric-field (E-field)-induced magnetic anisotropy and magnetization switching in CoNi/Pb(Mg1/3Nb2/3)O3– x PbTiO3(PMN-PT) magnetoelectric heterostructures. For CoNi/PMN-30%PT, the E-field-induced anisotropy shows a volatile behavior; whereas for CoNi/PMN-32%PT, a large and nonvolatile E-field-induced anisotropy field up to 54 kA/m is observed. These behaviors can be understood by measuring the strain versus the E-field curves of two kinds of substrates. On the basis of the E-field-induced nonvolatile magnetic switching, two stable magnetization states defined by applying E-field pulses were demonstrated in CoNi/PMN-32%PT heterostructure, which paves a new way for voltage-write magnetic random memory devices.

The L10 FePt–MgO/Fe–MgO bilayers were fabricated on thermal oxide silicon substrate by using magnetron sputtering. The TEM image shows that the FePt–MgO single layer has small and uniform granular grain. In the FePt–MgO/Fe–MgO bilayer system, with increasing Fe layer thickness, the grain size become larger and the grain boundary become obscure, while the magnetization process transforms from a coherent magnetization to an exchange spring behavior, and finally a two-phase magnetization reversible process.

In this work, the influence of the magnetoelastic field on the magnetic properties of FeCo thin film is analyzed by the micromagnetic model. Formula of magnetoelastic energy related to the stress between the FeCo and the underlayer are derived to analysis the role of stress on soft magnetic properties. The cubic anisotropy determines the symmetry of the loops. For the magnetoelastic field, the main term Hma has significant influence on the easy-axis coercivity and the cross term Hmb affects the slope of the hard-axis loop. Good in-plane anisotropy of FeCo thin film, which can be obtained by using certain underlayers (such as Cu, NiFe, CoFe), is corresponding to low value of Hma and Hmb. The magnetization 4πMs at amorphous grain boundary has great effect on the properties of FeCo film.

The L1(0) FePt (10 nm)/Fe (delta nm, delta = 0-15) bilayers were fabricated by using magnetron co-sputtering. The L1(0) FePt single layer shows good perpendicular orientation and the in-plane hysteresis loop shows almost a linear behavior. When delta is less than 3 nm, the FePt/Fe bilayers show behaviors like one magnetic phase, the coercivities are close to the values determined by Zeeman energy. When delta is larger than 3 nm, the in-plane hysteresis loops show behaviors similar to a soft magnetic film, the coercivities of the bilayers decreases slowly with the increasing Fe thickness because of confining by the exchange length of FePt layer and Fe layer. The measured coercivities values are optimally fitted by a 1/t(Fe)(1.15) relation. The magnetization reversal process and magnetic interaction were also investigated. (C) 2012 Elsevier B.V. All rights reserved.