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.

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.

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.

Spin valves Ta/(Ni 80 Fe 20 ) 60 Cr 40 /Co 70 Fe 20 Ni 10 /Cu/Co 70 Fe 20 Ni 10 /Ru/Co 70 Fe 20 Ni 10 /Fe 50 Mn 50 /Ta have been prepared by magnetron sputtering. It was found that the shift of low-field hysteresis loop with respect to H = 0 oscillates as the copper layer thickness changes. Structural studies showed the high perfection of the layer microstructure. Films of spin valves with the copper layer thickness corresponding to the second antiferromagnetic RKKI interaction maximum have been synthesized. They exhibit zero shift of low-field hysteresis loop and are characterized by high magnetoresistance effect. Sensing elements in the form of meanders prepared using the films demonstrate the almost anhysteretical field dependence of magnetoresistance and a magnetoresistive sensitivity of 0.5%/Oe.

Pseudo spin valve nanostructures, which comprise a dysprosium layer and exhibit giant magnetoresistance, are prepared by magnetron sputtering. The field dependences of magnetoresistance of the as-prepared nanostructures and nanostructures subjected to annealing and prolonged aging at room temperature were measured in a 83–333 K temperature range. Changes in the shape of magnetoresistance curves are used to identify changes in the magnetic state of the nanostructure. The microstructure of the nanostructures has been studied. Changes in the microstructure and magnetoresistive properties of pseudo spin valves were found, which are caused by annealing and storage. The results are interpreted on the assumption of the formation of Dy–Co–Fe ferromagnetic alloy at the CoFe/Dy interface.

Microsensors (meanders) were fabricated from spin valves with the composition TapeNi/RuiFeNi/CoFe/CuiCoFe/RuiCoFe/FeMn/Ta. Thermomagnetic treatment was used to modify a mutual orientation of magnetic anisotropy and shape anisotropy axes in sensor. Obtained magnetic configuration provides the anhysteretic magnetic reversal of meander. Meanders with different U-turns were investigated and difference in magnetic structure of such meanders was shown. Sensors with high magnetoresistive sensitivity and anhysteretic magnetic reversal were obtained. (C) 2018 Elsevier B.V. All rights reserved.

Metallic multilayer spin-valve nanostructures that comprise the exchange-coupled ferromagnet/ Ru/ferromagnet structure in the free layer have been synthesized by magnetron sputtering. For microobjects (meanders) formed from CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta spin valves with different thicknesses of ruthenium and copper layers, the dependences of the magnetoresistive sensitivity and low-field hysteresis loop shift on the meander strip width have been studied. Sensing elements characterized by high magnetoresistive sensitivity have been manufactured.

Spin-valve nanostructures with an exchange-coupled Gd/CoFe pair (synthetic ferrimagnet) as the free layer were prepared by magnetron sputtering. It was shown that when a fixed magnetic field is applied and the temperature near the compensation temperature of the synthetic ferrimagnet is varied, the spin valve switches between magnetic states, which are characterized by maximum and minimum resistance. The dependence of the compensation temperature on the Gd layer thickness is studied, which is interpreted based on the results of investigations of the microstructure of the Gd layer, taking into account peculiarities of its magnetic structure.

Spin valves that comprise synthetic antiferromagnet as a component of pinned layer and an exchange-coupled ferromagnet/Ru/ferromagnet structure in the free layer have been prepared by magnetron sputtering. Microobjects have been formed from spin valves by optical and electron-beam lithography. It has been shown that the shift of the low-field magnetoresistance hysteresis loop decreases as the thicknes of the Ru spacer in the free layer of spin valve increases. The almost hysteresis-free odd-field dependences of the magnetoresistance were obtained for micron-sized samples; in this case, the sensitivity is 0.2%/Oe.

Microobjects (strips) were formed by contact photolithography using Та/Ni80Fe20/Co90Fe10/Cu/Co90Fe10/Ru/Co90Fe10/Fe50Mn50/Ta spin-valves prepared by magnetron sputtering. A mutually perpendicular arrangement of uniaxial and unidirectional anisotropy axes in microobjects has been formed using two different thermomagnetic treatment regimes. The magnetoresistive sensitivity of spin valve and spin-valve-based microobject has been found to depend on the mutual arrangement of the easy magnetization axis and direction of magnetic field applied upon thermomagnetic treatment. The obtained data have been interpreted taking into account changes in the induced anisotropy and anisotropy due to the shape of the microobject.

FeMn-based spin valves with a gadolinium layer have been fabricated by magnetron sputtering. The magnetoresistive properties of the spin valves have been investigated at temperatures of 80–293 K. Temperature-induced switching between low- and high-resistance magnetic states has been revealed. Realization of the low- or high-resistance states depends on which magnetic moment dominates in the exchange-coupled Gd/CoFe, of Gd or CoFe. It has been shown that the switching temperature depends on the thickness of the gadolinium layer.

The deviation of the pinning direction from the easy axis was created in spin valves by thermomagnetic treatment. The angle between the uniaxial and the unidirectional magnetic anisotropy axes is shown to depend on the value of the field applied during the thermomagnetic treatment. Anhysteretic dependence of magnetoresistance on the magnetic field is obtained for the spin valves with crossed anisotropy configuration. The interval within which the magnetic field dependence of magnetoresistance is linear depends on the spacer thickness.

The microstructure and the magetoresistive characteristics of [NiFeCo/Cu] 8 superlattices prepared by magnetron sputtering with various thickness of the buffer NiFeCr layer and exhibiting a giant magnetoresistive effect have been studied. It has been found that these nanostructures are formed with a strong or weak hysteresis depending on the structure (bcc or fcc) formed in the NiFeCr buffer layer. The method of the substantial decrease in the hysteresis loop width of the magnetoresistance by using the composite Ta/NiFeCr buffer layer has been suggested.