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We consider a spin valve composed of a superconducting film (S) between two ferromagnetic insulators (FI) on two sides. In the dirty limit, the superconductor is described by Usadel equations. Appropriate boundary conditions were chosen for two S-FI interfaces, which are described via the interface parameter spin mixing angle. By numerically solving the Usadel equations, the density of states (DOS) at different spin mixing angles was obtained. It was shown previously that the critical temperature of such an FI-S-FI structure depends on the mutual alignment of the FI layers’ magnetization. We follow the evolution of DOS at the change of misalignment of ferromagnets magnetization and probe the zero bias peak creation. The DOS characteristic features may give fruitful information about triplet superconducting components creation and interplay inside the S layer. [ABSTRACT FROM AUTHOR]

For microobjects based on spin valves, changes in the magnetic state are observed under the action of short-term direct current. It has been shown that the magnetic moment of the free layer rotates when a certain current density is attained. The rotation angle grows with increasing current density. The magnetic moment rotates predominantly due to the thermal effect of current. Rotation angle changes caused by spin accumulation in Ta or NiFeCr layers and the transfer of the spin-orbit torque of electrons to the magnetic moment of the free layer have been revealed. [ABSTRACT FROM AUTHOR]

In chemistry and biochemistry, chirality represents the structural asymmetry characterized by nonsuperimposable mirror images for a material such as DNA. In physics, however, chirality commonly refers to the spin–momentum locking of a particle or quasiparticle in the momentum space. While seemingly disconnected, structural chirality in molecules and crystals can drive electronic chirality through orbital–momentum locking; that is, chirality can be transferred from the atomic geometry to electronic orbitals. Electronic chirality provides an insightful understanding of chirality-induced spin selectivity, in which electrons exhibit salient spin polarization after going through a chiral material, and electrical magnetochiral anisotropy, which is characterized by diode-like transport. It further gives rise to new phenomena, such as anomalous circularly polarized light emission, in which the light handedness relies on the emission direction. These chirality-driven effects will generate broad impacts for fundamental science and technology applications in spintronics, optoelectronics, and biochemistry. [ABSTRACT FROM AUTHOR]

Today’s semiconductor devices use the charges of electrons and holes for tasks like light emission and signal processing. Semiconductor spintronics, a newer field, aims to exploit the spin of charge carriers to advance technologies like magnetic lasers, sensors, and transistors. Spintronics could enable the creation of memory, sensing, and logic devices with capabilities that charge-based devices can't match. This work explores the progress made with spintronic materials and devices, their current uses, and what the future might hold. A key feature of emerging spintronic logic devices is their ability to generate highly spin-polarized currents in two- and three-terminal tunnel junctions, which can lead to devices that consume much less power than traditional charge-based ones. Recent advancements in material engineering give hope for the rapid development and deployment of these new spintronic technologies.

The properties of a superconducting spin valve based on Fe1/Fe2/Pb prepared on a PMN-PT piezoelectric substrate ([Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3) in external magnetic and electric fields were studied. A shift in superconducting transition temperature more than 200 mK was observed when the mutual direction of the magnetizations of the ferromagnetic layers changed from antiparallel to perpendicular orientations in an external magnetic field. The possibility of realizing the full effect of a superconducting spin valve was demonstrated. It was established that the shift in superconducting transition temperature increased with an increase in the value of the applied electric field to the PMN-PT piezoelectric substrate. [ABSTRACT FROM AUTHOR]

Today’s semiconductor devices use the charges of electrons and holes for tasks like light emission and signal processing. Semiconductor spintronics, a newer field, aims to exploit the spin of charge carriers to advance technologies like magnetic lasers, sensors, and transistors. Spintronics could enable the creation of memory, sensing, and logic devices with capabilities that charge-based devices can't match. This work explores the progress made with spintronic materials and devices, their current uses, and what the future might hold. A key feature of emerging spintronic logic devices is their ability to generate highly spin-polarized currents in two- and three-terminal tunnel junctions, which can lead to devices that consume much less power than traditional charge-based ones. Recent advancements in material engineering give hope for the rapid development and deployment of these new spintronic technologies. [ABSTRACT FROM AUTHOR]

The paper proposes a model of an electromagnetic radiation sensor that uses the precession of the magnetization vector in a ferromagnet (ferromagnetic resonance) as a result of absorbing the energy of an incident electromagnetic wave, the generation of a spin current as a result of this precession, the generation of a spin-polarized current as a result of the passage of a spin current in a non-magnetic metal, and a change in the direction of magnetization of a ferromagnetic layer with a low coercive force (free layer) due to the passage of a spin-polarized current. Then the radiation will be detected by its effect on the electrical resistance of the entire structure, which depends on the mutual directions (parallel or antiparallel) of magnetization of the free and fixed (with a large coercive force) ferromagnetic layers (phenomenon of giant magnetic resistance). The dependence of the spin-polarized current in the device on the frequency and amplitude of the incident electromagnetic wave with linear polarization was calculated. A method of calculating the range of amplitude and frequency values of radiation that can be detected by the sensor has been developed. The parameters of this model are the detection time and the number of spin gates in one sensor. Calculations are given for a ferromagnetic layer made of permalloy and for spin valves with four different critical current values that determine the process of remagnetization of the free layer: 20, 50, 100, and 200 microamps.

Spin valves with a synthetic antiferromagnet were fabricated via magnetron sputtering. It was shown that the fabricated spin valve layers had a perfect microstructure and smooth interfaces, and therefore, an RKKY interaction dominated in the coupling of the ferromagnetic layers separated by a copper spacer. Rhombus-shaped micro-objects were fabricated from a single spin valve film. The thermomagnetic treatment procedure was found to form unidirectional anisotropy in the micro-object such that the values of the exchange bias fields in the rhombus' nonparallel sides were opposite in sign. For the CoFeNi/Ru/CoFeNi synthetic antiferromagnet, we determined the differences between the ferromagnetic layer thicknesses at which the thermomagnetic treatment formed the same exchange bias all over each rhombus' side. We also fabricated a sensor element in which each side of the rhombus was the shoulder of a Wheatstone bridge. After the thermomagnetic treatment procedure, each shoulder worked as an active magnetosensitive element, enabling the device to operate as a full Wheatstone bridge. The sensor output exhibited a step shape, high sensitivity to field changes, and significant magnetic hysteresis. Such characteristics are suitable for switching devices. [ABSTRACT FROM AUTHOR]

[Display omitted] In recent years, enormous efforts have been made to identify and manipulate the exotic electrical and magnetic properties at a two-dimensional (2D) limit of various exciting materials. The spin–orbit coupling (SOC) in 2D van der Waals (vdW) heterostructures opens a fascinating and versatile platform to implement the intriguing quantum-engineered spintronic devices for practical applications. This review comprehensively outlines the modern-era progress of investigating the inherent magnetism of atomically thin 2D materials. Firstly, in this review, the most recent developments of synthesis, characterizations, functionalities, and spin textures in 2D magnetic materials are summarized in detail. Secondly, we conferred the well-known phenomena related to the proximity effect, spin–orbit torque (SOT), spin valve magnetic tunnel junction (MTJ), spin field effect transistor (FET) and magneto memristive-based applications. In addition, we also explored the possible interplay between 2D magnetic materials and associated band topology for spin caloritronics. Finally, we provided our perspective on the recent and upcoming challenges and goals of this promising research area, which leads the 2D magnetic materials to the modern era of energy-efficient quantum computing. [ABSTRACT FROM AUTHOR]

How to control the charge and spin in nanodevices is an important topic in spintronics. In this letter, we theoretically propose a spin diode and spin valve (SV) device controlled by all-electrical means, which is composed of a quantum dot (QD) coupled to a pair of nonmagnetic electrodes. When both electric charge bias and spin bias exist within the device, the I – V curves of this device exhibit an asymmetric distribution, and this asymmetry can be manipulated by the gate voltage. More interestingly, if we apply an external magnetic field on the QD, we can observe significant high- and low-resistance state switching with respect to the magnetic field, which can function as a SV device. This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing. [ABSTRACT FROM AUTHOR]

We have theoretically studied the transport properties of the SIsN S O F structure consisting of thick (S) and thin (s) films of superconductor, an insulator layer (I), a thin film of normal metal with spin–orbit interaction (SOI) (N S O ), and a monodomain ferromagnetic layer (F). The interplay between superconductivity, ferromagnetism, and spin–orbit interaction allows the critical current of this Josephson junction to be smoothly varied over a wide range by rotating the magnetization direction in the single F-layer. We have studied the amplitude of the spin valve effect and found the optimal ranges of parameters. [ABSTRACT FROM AUTHOR]

We have studied the influence of the piezoelectric properties of the PMN-PT substrate ([Pb(Mg1/3Nb2/3)O3]1-x – [PbTiO3]x where x = 0.29 − 0.31) on the properties of the superconducting spin valve Fe/Al/Co/Pb exposed to electric and magnetic fields. According to the research results, with an increase in the applied electric field to the PMN-PT substrate, it is possible to register an increase in the shift of the superconducting transition temperature of the superconducting spin valve Fe/Al/Co/Pb. The maximum shift was 36 mK when an electric field of 1 kV/cm was applied, which was half of the superconducting transition width. The shift of the superconducting transition temperature equal to 255 mK in a magnetic field was recorded, and thus the possibility of a full superconducting spin valve effect was shown. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs), a prominent type of spintronic device based on the spin valve effect, have facilitated the development of numerous spintronic applications. The technical appeal for the next‐generation MTJ devices has been proposed in two directions: improving device performance by utilizing advanced two‐dimensional (2D) ferromagnetic materials or extending device functionalities by exploring the gate‐tunable magnetic properties of ferromagnets. Based on the recent development of 2D magnets with the ease of external stimuli, such as electric field, due to their reduced dimensions, reliable prospects for gate‐tunable MTJ devices can be achieved, shedding light on the great potential of next‐generation MTJs with multiple functionalities for various application environments. While the electrical gate‐tunable MTJ device is highly desirable for practical spintronic devices, it has not yet been demonstrated. Here, we demonstrate the experimental realization of a spin valve device by combining a vertical Fe3GeTe2/h‐BN/Fe3GeTe2 MTJ with an electrolyte gate. The magnetoresistance ratio (MR ratio) of 36% for the intrinsic MTJ confirms the good performance of the device. By electrolyte gating, the tunneling MR ratio of Fe3GeTe2/h‐BN/Fe3GeTe2 MTJ can be elevated 2.5 times, from 26% to 65%. Importantly, the magnetic fields at which the magnetoresistance switches for the MTJ can be modulated by electrical gating, providing a promising method to control the magnetization configuration of the MTJ. Our work demonstrates a gate‐tunable MTJ device toward the possibility for gate‐controlled spintronic devices, paving the way for performing 2D magnetism manipulations and exploring innovative spintronic applications. [ABSTRACT FROM AUTHOR]

Spin valves containing a Dy layer have been formed on an elastic polyimide film by magnetron sputtering. The field dependences of the magnetoresistance of samples subjected to different tensile deformations have been measured. The character of the variations of the magnetoresistive properties of a spin valve subjected to tensile deformation is shown to depend on the thickness of the dysprosium layer. In particular, the thickness of the dysprosium layer affects the maximum relative elongation at which the magnetoresistance of spin valves remains unchanged. [ABSTRACT FROM AUTHOR]

Abstract Magnetic tunnel junctions (MTJs), a prominent type of spintronic device based on the spin valve effect, have facilitated the development of numerous spintronic applications. The technical appeal for the next‐generation MTJ devices has been proposed in two directions: improving device performance by utilizing advanced two‐dimensional (2D) ferromagnetic materials or extending device functionalities by exploring the gate‐tunable magnetic properties of ferromagnets. Based on the recent development of 2D magnets with the ease of external stimuli, such as electric field, due to their reduced dimensions, reliable prospects for gate‐tunable MTJ devices can be achieved, shedding light on the great potential of next‐generation MTJs with multiple functionalities for various application environments. While the electrical gate‐tunable MTJ device is highly desirable for practical spintronic devices, it has not yet been demonstrated. Here, we demonstrate the experimental realization of a spin valve device by combining a vertical Fe3GeTe2/h‐BN/Fe3GeTe2 MTJ with an electrolyte gate. The magnetoresistance ratio (MR ratio) of 36% for the intrinsic MTJ confirms the good performance of the device. By electrolyte gating, the tunneling MR ratio of Fe3GeTe2/h‐BN/Fe3GeTe2 MTJ can be elevated 2.5 times, from 26% to 65%. Importantly, the magnetic fields at which the magnetoresistance switches for the MTJ can be modulated by electrical gating, providing a promising method to control the magnetization configuration of the MTJ. Our work demonstrates a gate‐tunable MTJ device toward the possibility for gate‐controlled spintronic devices, paving the way for performing 2D magnetism manipulations and exploring innovative spintronic applications.

The utilisation of quantum properties can largely impact how technological devices work. Up to date, the acquired knowledge of the quantum nature of several systems inspired the proposal of several novel technologies such as quantum sensing, quantum simulation and quantum computing. Single Molecule Magnets (SMMs) represent a class of quantum objects with promising properties to be exploited in quantum technologies. As of today, SMMs have been shown to possess bewildering quantum effects such as Quantum Tunnelling of the Magnetisation (QTM), quantisation of the energy manifold, coherence, spin parity effects and entanglement, among others. Furthermore, they have been successfully integrated into hybrid single-molecule spintronic devices, such as spin transistors and spin valves, hence, propitiating extensive investigation of technological applications. In this Review Article, some key quantum aspects, which make SMMs promising systems for technological proposals, are revised. Moreover, single-molecule devices, in which SMMs have been integrated in hybrid devices, as well as the technological applications such as quantum sensing, quantum simulation and quantum computing are described.

The utilisation of quantum properties can largely impact how technological devices work. Up to date, the acquired knowledge of the quantum nature of several systems inspired the proposal of several novel technologies such as quantum sensing, quantum simulation and quantum computing. Single Molecule Magnets (SMMs) represent a class of quantum objects with promising properties to be exploited in quantum technologies. As of today, SMMs have been shown to possess bewildering quantum effects such as Quantum Tunnelling of the Magnetisation (QTM), quantisation of the energy manifold, coherence, spin parity effects and entanglement, among others. Furthermore, they have been successfully integrated into hybrid single-molecule spintronic devices, such as spin transistors and spin valves, hence, propitiating extensive investigation of technological applications. In this Review Article, some key quantum aspects, which make SMMs promising systems for technological proposals, are revised. Moreover, single-molecule devices, in which SMMs have been integrated in hybrid devices, as well as the technological applications such as quantum sensing, quantum simulation and quantum computing are described.

Spin valves with a CoFe/Dy/CoFe composition in the lower part of their structure have been manufactured by magnetron sputtering. The effect of prolonged storage and temperature on the structure and magnetotransport properties of spin valves has been studied. The change in the compensation temperature was used as an indicator of the intensity of diffusion processes in the exchange-coupled CoFe/Dy/CoFe structure. It has been revealed that diffusion induced changes in the magnetotransport properties become smaller with a decrease in the dysprosium layer thickness. It has been shown that the nanostructure still contains pure dysprosium, the atoms of which do not participate in the sperimagnetic ordering of the Dy–Co–Fe interface, even at a small nominal thickness (4 nm) of the dysprosium layer 3 months after sputtering. [ABSTRACT FROM AUTHOR]

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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]

This work is a study of the formation processes and the effect of related process parameters of multilayer nanosystems and devices for spintronics. The model system is a superconducting spin valve, which is a multilayer structure consisting of ferromagnetic cobalt nanolayers separated by niobium superconductor nanolayers. The aim was to study the influence of the main technological parameters including temperature, concentration and spatial distribution of deposited atoms over the nanosystem surface on the atomic structure and morphology of the nanosystem. The studies were carried out using the molecular dynamics method using the many-particle potential of the modified embedded-atom method. In the calculation process the temperature was controlled using the Nose–Hoover thermostat. The simulation of the atomic nanolayer formation was performed by alternating the directional deposition of different composition layers under high vacuum and stationary temperature conditions. The structure and thickness of the formed nanolayers and the distribution of elements at their interfaces were studied. The alternating layers of the formed nanosystem and their interfaces are shown to have significantly different atomic structures depending on the main parameters of the deposition process.

Exchange-coupled spin valves based on ferromagnetic alloys CoFeNi and antiferromagnetic alloy FeMn are obtained on flexible polyimide substrates by magnetron sputtering. The magnetoresistive properties of films and microstrips of spin valves are measured at various degrees of bending deformation of the sample. The behavior of the dependence of the deformation sensitivity of the spin valve on the interaction between the magnetic layers and on the arrangement of the anisotropy axes with respect to the deformation vector is characterized. It is found that the deformation sensitivity decreases with an increase in the interval between the fields of magnetization reversal of the free and fixed layers in the spin valve. [ABSTRACT FROM AUTHOR]

Exchange-biased nanostructures of the "spin valve" type, which include an additional layer of the rare-earth metal dysprosium, are made by magnetron sputtering. Temperature variations in the magnetotransport properties of the spin valves are used as an indicator of change in the magnetic state of the dysprosium nanolayer. Information on the formation of unidirectional magnetic anisotropy at the CoFe/Dy interface upon the transition through Néel temperature of dysprosium is obtained. It is shown that the antiferromagnetic phase in the polycrystalline dysprosium layer has noncollinear magnetic ordering. The temperature dependence of the angle between the directions of the magnetic moments at the dysprosium-layer boundaries is determined. The change in this angle observed in the entire temperature region of the existence of helicoidal ordering in dysprosium reflects the change in the period of the magnetic helicoid in dysprosium with temperature. Thus, a new method for studying chiral magnetics is proposed, in which the indicator of the helicoidal magnetic state is a spin valve possessing giant magnetoresistance, containing a layer of the helimagnet under investigation. [ABSTRACT FROM AUTHOR]

The key to achieving high-quality and practical van der Waals heterostructure devices made from various two-dimensional (2D) materials lies in the efficient control over clean and flexible interfaces. Inspired by the “movable-type printing”, one of the four great inventions of ancient China, we demonstrate the “movable-type” transfer and stacking of 2D materials, which utilizes prefabricated polyvinyl alcohol (PVA) film to engineer the interfacial adhesion to 2D materials, and provides a flexible, efficient and batchable transfer scheme for 2D materials. The experiments also verify the “movable-type” transfer can preciously control the position and orientation of 2D materials, which meets the burgeoning requirements such as the preparation of twisted graphene and other heterostructures. Importantly, water-solubility of PVA film ensures an ideal interface of the materials without introducing contamination. We illustrate the superiority of this method with a WSe2 vertical spin valve device, whose performance verifies the applicability and advantages of such a method for spintronics. Our PVA-assisted “movable-type” transfer process may promote the development of high-performance 2D-material-based devices.

A Ti2NiAl inverse Heusler alloy based current-perpendicular-to-plane (CPP) spin valve (SV) with various kinds of atomic terminated interfaces has been designed to explore the potential application of Heusler alloys in spintronics devices. By performing first principles calculations combined with the nonequilibrium Green’s function, it is revealed that spin magnetic moments of interfacial atoms suffer a decrease, and the electronic structure shows that the TiNiB-terminated structure possesses the largest interface spin polarization of ≈55%. Our study on spin-transport properties indicates that the total transmission coefficient at the Fermi level mainly comes from the contribution from the spin up electrons, which are regarded as the majority of the spin electrons. When the two electrodes of the CPP-SV device are in parallel magnetization configuration, the interface containing Ti and Ni atoms possesses a higher spin up transmission coefficient than the interface containing Ti and Al atoms. The device with the TiNiB-terminated interface possesses the largest magnetoresistance ratio of 3.28 × 105, and it has great application potential in spintronics devices.

We present a study of magnetic structures with controllable effective exchange energy for Josephson switches and memory applications. As a basis for a weak link we propose to use a periodic structure composed of ferromagnetic (F) layers spaced by thin superconductors (s). Our calculations based on the Usadel equations show that switching from parallel (P) to antiparallel (AP) alignment of neighboring F layers can lead to a significant enhancement of the critical current through the junction. To control the magnetic alignment we propose to use a periodic system whose unit cell is a pseudo spin valve of structure F1/s/F2/s where F1 and F2 are two magnetic layers having different coercive fields. In order to check the feasibility of controllable switching between AP and P states through the whole periodic structure, we prepared a superlattice [Co(1.5 nm)/Nb(8 nm)/Co(2.5 nm)/Nb(8 nm)]6 between two superconducting layers of Nb(25 nm). Neutron scattering and magnetometry data showed that parallel and antiparallel alignment can be controlled with a magnetic field of only several tens of Oersted.

The dependence of the Neel temperature on the thickness of the dysprosium layer has been studied. It is shown that the temperature range within which the paramagnetic–antiferromagnetic phase transition takes place depends on the microstructure and thickness of the dysprosium layer. Spin valves based on a CoFe alloy with dysprosium as an antiferromagnetic layer are manufactured via magnetron sputtering. It is shown that unidirectional anisotropy forms in the CoFe/Dy interface. The direction of the exchange bias field depends on the direction of the magnetic moment of the CoFe layer in the formation of exchange coupling. [ABSTRACT FROM AUTHOR]

Magnetic sensor with spin valve-GMR technology with medium dynamic range is designed for a diversity of applications, including linear and rotary position measurements, proximity switches, and current sensors. For this, the sensing layer (SL) of the spin valve stack was modified by a soft pinning layer (SPL) through an exchange bias field created by an antiferromagnetic layer which has a lower blocking temperature than the one that is kept adjacent to the pinned layer. Numerical simulation was carried out to control the bias field by keeping a non-magnetic Ru spacer layer between the SPL and SL layers and the results were experimentally verified. The magnetic sensor was fabricated with linear operating field range of the order ±100 Oe having a sensitivity of the order of 0.1 m V V -1 Oe -1 near zero field. The thermal performance confirms that the device can be operated in the temperature range of -40 ∘ C to 125 ∘ C and it has a thermal coefficient of voltage around 15 µ V V -1∘ C -1 ., (© 2024 IOP Publishing Ltd.)

π-Conjugated semiconductors, primarily composed of elements with low atomic number, are regarded as promising spin-transport materials due to the weak spin–orbit coupling interaction and hence long spin relaxation time. Moreover, a large number of additional functions of organic semiconductors (OSCs), such as the abundant photo-electric properties, flexibility, and tailorability, endow the organic spintronic devices more unique properties and functionalities. Particularly, the integration of the photo-electric functionality and excellent spin transport property of OSCs in a single spintronic device has even shown great potential for the realization of spin manipulation in OSCs. In this review, the application of OSCs in spintronic study will be succinctly discussed. As the most important and extensive application, the long-distance spin transport property of OSCs will be discussed first. Subsequently, several multifunctional spintronic devices based on OSCs will be summarized. After that, the organic-based magnets used for the electrodes of spintronic devices will be introduced. Finally, according to the latest progress, spin manipulation in OSCs via novel spintronic devices together with other prospects and challenges will be outlined.

We have studied superconducting properties of spin-valve thin-layer heterostructures CoOx/F1/Cu/F2/Cu/Pb in which the ferromagnetic F1 layer was made of Permalloy while for the F2 layer we have taken a specially prepared film of the Heusler alloy Co2Cr1−xFexAl with a small degree of spin polarization of the conduction band. The heterostructures demonstrate a significant superconducting spin-valve effect, i.e., a complete switching on and off of the superconducting current flowing through the system by manipulating the mutual orientations of the magnetization of the F1 and F2 layers. The magnitude of the effect is doubled in comparison with the previously studied analogous multilayers with the F2 layer made of the strong ferromagnet Fe. Theoretical analysis shows that a drastic enhancement of the switching effect is due to a smaller exchange field in the heterostructure coming from the Heusler film as compared to Fe. This enables to approach an almost ideal theoretical magnitude of the switching in the Heusler-based multilayer with a F2 layer thickness of ca. 1 nm.

Spin valves with holmium layers and three-layer structures metal/Ho/metal were prepared by magnetron sputtering. A holmium layer in the spin valves is polycrystalline with weak axial <002> texture. The structural coherence length along the hexagonal c-axis is approximately 2/5 of the total thickness of the holmium layer. Field dependences of the spin valves magnetoresistance were measured at different temperatures. Correlation was revealed between magnetic state in holmium layer and the shape of magnetoresistive curve. Deviation of magnetic moments of the reference layer and the adjacent part of holmium from the applied magnetic field was investigated. The field induced mobility of the magnetic helicoid in holmium layers was revealed. Image 1 • Neel temperature of Ho layer depends on the thickness and microstructure perfection. • Antiferromagnetic Ho layer carries out exchange bias in the adjacent ferromagnetic. • Spin valve magnetoresistance correlates with the magnetic state in Ho layer. • Period of the magnetic helicoid in Ho layer varies with temperature. • The magnetic helicoid in Ho layer is rotated around c-axis by magnetic field. [ABSTRACT FROM AUTHOR]

In spin valve sensors, the bias point caused by the interlayer coupling between the pinned layer and the free layer is a crucial issue encountered in the design process, which degrades the responsivity and the weak-field detection feature. In tackling this issue, we present the magnetic bias technique for efficient control of the bias point of the pinned spin valve (PSV). Specifically, the magnetic field that creates a shift of the bias point is generated by a coil being wrapped around the PSV devices. The PSV multilayer structure, Ta(5 nm)/NiFe(3 nm)/CoFe(4.5 nm)/Cu(1.5 nm)/CoFe(2.4 nm)/IrMn(10 nm)/Ta(5 nm), was fabricated using DC magnetron sputtering deposition. The PSV devices patterned by using a simple lift-off technique have a dimension of 1.5 µm × 200 µm. The bias magnetic field was tuned between ± 5 mT by changing an external DC current. Our experimental results indicate that the bias point can be efficiently controlled via a simple adjustment of the current in the bias coil. Consequently, the device responsivity was remarkably enhanced by a factor of 6.75, from 0.8 V/T to 5.4 V/T, leading to a decrease of the detectivity (field noise) from 366 nT/√Hz@1 Hz to 108 nT/√Hz@1 Hz. Additionally, the field noise was further suppressed by a factor of 5 from 363 nT/√Hz@1 Hz to 72 nT/√Hz@1 Hz by applying the AC-driven mode in the half-bridge PSV. The simplicity of our proposed technique makes it particularly pertinent to PSV sensor designs for low-field applications. [ABSTRACT FROM AUTHOR]

A method of universal thermomagnetic treatment forming a pairwise opposite exchange bias in spin valves, which are sensor elements of a Wheatstone bridge, has been developed. The method is based on the formation of two magnetic phases in a spin valve upon the transition of a synthetic antiferromagnet into a spin-flop state. Thermomagnetic treatment in a two-phase state leads to the formation of a pairwise mutually opposite exchange bias in different elements of a Wheatstone bridge. The direction of a formed exchange bias is governed by the uniaxial anisotropy of every element. [ABSTRACT FROM AUTHOR]