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.

Structural and magnetoresistive properties of multilayer Co77Fe17Ni6/Cu and Co77Fe17Ni6/Cu96In4 nanostructures with a number of magnetic layers and nonmagnetic interlayers of 1 to 11 are studied. The sharp axial 〈111〉 texture and more perfect interfaces are shown to form in the nanostructures with Cu96In4 interlayers, and a relatively small magnetoresistance hysteresis is observed. Atomic force microscopy is used to estimate the surface roughness and crystallite size of the samples under study. As the number of layers in the Cu96In4-based samples increases, the crystallite size is found to slightly change from layer to layer in the range of 18–22 nm, whereas, for the Cu-based sample, the crystallite size substantially increases. For superlattices with Cu interlayers, the 10-fold decrease in the magnetoresistance is observed as the thickness of Co77Fe17Ni6 layers slightly, namely, from 1.5 to 2 nm increases.

An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X23550021

Structure and morphology of epitaxial [Fe/Cr](30 )multilayers with ultrathin Fe layers (nominally 0.12 nm and 0.08 nm) have been investigated by X-ray reflectivity, synchrotron Mo center dot ssbauer spectroscopy at low temperature and grazing-incidence small angle X-ray scattering (GISAXS). The films demonstrate Kondo-like behavior of electrical resistivity. The GISAXS patterns reveal their cluster-layered structure. The observed side maxima give the information about the sizes and distances between lateral inhomogeneities. Mossbauer reflectivity spectra measured below the critical angle of the total reflection support the existence of the cluster-layered structure of the samples. Magnetic hyperfine field distributions show that largest number of 57Fe atoms is situated in interfaces of iron clusters and their number increases in the thinnest films.

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.

The injection of a pure spin current into a conducting helimagnet is investigated. The characteristic decay lengths for the spin current injected into the helimagnet are determined, and their physical meaning is described. It is shown that instead of the spin diffusion length, helimagnets are characterized by the decay length that is always smaller than the spin diffusion length, the difference in these lengths being determined by the ratio of the helimagnet spiral period to the spin diffusion length. We predict the existence of the “effect of the chiral polarization of a pure spin current,” i.e., the emergence of the spin current with longitudinal (transverse) polarization, which depends on the spiral chirality, upon the injection of a pure spin current with the transverse (longitudinal) polarization relative to the spiral axis.

We construct a nonlinear theory of electric resistance of chiral helimagnets, in which the shape changes and the magnetization spiral starts rotating during the passage of electric current due to the spin transfer torque effect. It is shown that the rotation of the spin spiral under the action of the passing current, the electric resistance of the helimagnet is always lower than the resistance of a helimagnet in which the spin spiral is stationary. It is found that the current–voltage characteristic of the helimagnet in the presence of the spin transfer torque from the conduction electron system to the system of localized electrons can be essentially nonlinear. The possibility of the spin electric bistability effect in helimagnets is predicted for the situation when the spin contribution to electric resistance of a helimagnet can take two different values for the same value of the current passing through it. The possibility of realization of states with a negative differential resistance in helimagnets is demonstrated.

Flexible spin valves were prepared by magnetron sputtering on polyimide substrates. The buffer layer that reduces significantly the effect of the polymer substrate on the spin valve microstructure and magnetoresistive properties was revealed. Bending deformation was applied to the microobjects based on the flexible spin valves in parallel to anisotropy axes. It was revealed that during the bend the magnetoresistance changes due to the joint impact of both the change of the magnetic field projection on the film plane and the change of the magnetic properties of the ferromagnetic layers. The obtained dependences have been used in construction of bending sensor, in which the flexible spin valve microstripes were united into the Wheatstone bridge.

Dysprosium nanolayers differing in the thickness are prepared by magnetron sputtering on Al2O3(R) substrates using Co90Fe10, β-Ta, and Nb buffer layers. The correlation between the crystallographic texture type and peculiarities of temperature dependences of electrical resistance of polycrystalline dysprosium films is studied. It is found that, in the case of deposition of Dy directly on Al2O3(R), a two-component texture forms in the rare-earth metal layer. One of the components is characterized by the hexagonal axis parallel to the film plane, whereas the other component is characterized by the axis perpendicular to the film plane. In the case of deposition of Dy on the β-Ta buffer layer, the microstructures of Al2O3 and Dy are shown to demonstrate the matching through β-Ta, and the perfection of the two-component texture increases. In the antiferromagnetic state, the texture components become “phases” differing in the orientation of magnetic helicoid axis, and the anitiferromagnetic ordering occurs at different temperatures.

A theory of spin and charge transport in bounded metallic magnets has been constructed, which takes into account the effects of spin-orbit scattering of conduction electrons by crystal lattice defects. The theory can be used to describe the spin Hall effect and the anomalous Hall effect and can serve as a basis for describing the phenomena of spin-orbitronics. Phenomenological boundary conditions for the charge and spin fluxes at the interface between two different metals have been formulated, on the basis of which the injection of a pure spin current into a helimagnet, which arises in a normal metal as a manifestation of the spin Hall effect, is described. The existence of an “effect of chiral polarization of a pure spin current” is predicted, which consists in the appearance in a helimagnet of a longitudinally polarized pure spin current and a longitudinal component of the nonequilibrium electron magnetization, depending on the chirality of the helimagnet helix, upon injection of a transversely polarized spin current from a normal metal.

Rhombus-shaped microobjects formed by strips of two micrometers wide were fabricated from the spin valve film. The influence of the shape anisotropy on the layers magnetic moment rotation during the spin valve magnetic reversal is studied. A method for two-stage thermomagnetic treatment in a direction-fixed magnetic field has been found. The method allows to obtain the opposite sign values of the exchange bias fields in the non-parallel rhombus sides. The direction of the formed exchange bias is determined by the deviation of the strip from the uniaxial anisotropy axis and from the magnetic field applied during thermomagnetic treatment. Based on a rhombus-shaped microobject made from a single spin valve film, the device is a Full Wheatstone bridge. Each side of the rhombus is an active magnetically sensitive element.

The Ta/Dy/Ta nanostructures are fabricated by high-vacuum magnetron sputtering. Resistance and longitudinal magnetoresistance are measured. It is shown that the observed the effect of magnetic field on resistance are due to the competition of two effects of different nature. The negative isotropic magnetoresistance in the dysprosium layer is due to the alignment of local magnetic moments in the direction of the applied magnetic field. The positive longitudinal magnetoresistance in tantalum layers is caused by a change in the conditions of scattering of electrons during the accumulation of electrons with opposite spins on opposite surfaces of the metal film with strong spin-orbit coupling.

A quantum theory of electron spin transport in conductive magnets is developed. The theory describes a large number of effects that arise due to spin-orbit scattering of conduction electrons on crystal lattice defects, such as the spin Hall effect, the inverse spin Hall effect, and the anomalous Hall effect. The transport through the contact of two different conductive magnetics is also considered; the phenomenological boundary conditions for the charge and spin flows are formulated, which make it possible to take into account the spin flip at the interface. The developed electron spin transport theory is used to describe the spin-orbitronics of the “helimagnet metal/non-magnetic metal” heterojunction. The spatial distribution of the polarization of the spin current injected into the helimagnet is found, and the characteristic decay lengths of different components of the polarization vector of the spin current are determined.

An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X23550021

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.

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 valvesubjected 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 magnetoresistanceof spin valves remains unchanged.

The influence of the state of interfaces on the magnetoresistive properties of Co/Cu superlattices has been studied by the methods of nuclear magnetic resonance and X-ray reflectometry. It has been found that the magnetron-sputtered superlattices with the highest value of the giant magnetoresistance effect have the largest fraction of highly perfect Co/Cu interlayer boundaries, as well as practically the smallest fraction of cobalt atoms localized in the interfaces.