Melt-spun ribbons of GdTbDyHoEr high-entropy alloy have a single-phase hexagonal-close-packed structure. The maximum value of the magnetic entropy change ΔSM for this alloy after rapid quenching increases up to 8.6 J kg− 1 K− 1 in the external magnetic field of 5 T at T = 180 K, and the refrigerant capacity RC reaches 340 J kg− 1 in the external magnetic field of 2 T. The present analysis indicates that the higher values of the magnetic entropy change and the refrigerant capacity for the GdTbDyHoEr melt-spun ribbons are apparently due to their lower effective magnetic anisotropy in comparison with the bulk alloy and more intense response to an external magnetic field. The presented results indicate a way to obtain highly efficient materials for magnetic refrigeration applications.

The bulk GdTbDyHoEr magnetic high-entropy alloy is prepared by induction melting; the same alloy in the form of ribbons is prepared by rapid quenching from the melt. Peculiarities of the structure and magnetic and magnetocaloric properties of these materials are analyzed. The both states of the alloy are characterized by the hexagonal structure. The magnetic entropy change ΔSM is determined using measured magnetic isotherms and Maxwell’s relations. The maximum ΔSM is observed at 175 K and, for a magnetic field change of 2 T, it is 1.8 and 2.6 J/kg К for the bulk and rapidly quenched alloys, respectively. Taking into account the determined parameters of magnetocaloric effect, the alloys show promise as materials for applications in magnetic refrigeration devices.

Magnetic properties of amorphous Gd-Co ferrimagnetic films prepared by magnetron sputtering have been studied for various thicknesses. In a certain temperature range close to the magnetic compensation temperature, triple hysteresis loops and the characteristic features of the tempera-ture dependencies of magnetization were observed for all samples under consideration. Two-layer film model with an inhomogeneous chemical composition and a spin-flop transition scenario in two sub-lattice ferrimagnet was employed for understanding the origins of these phenomena. Within the framework of the spin-flop transition, the inter sub-lattice exchange coupling constant was estimated using various methods.

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.

Triple hysteresis loops were observed for amorphous ferrimagnetic Gd-Co films near the magnetic compensation temperature, which can be a consequence of both the spin-flop transition and the chemical composition gradient. In the work, an assessment of the possible chemical inhomogeneity of the films based on magnetic measurements was carried out and its relationship with the thickness of the samples was observed.

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.

Triple hysteresis loops were observed for amorphous ferrimagnetic Gd-Co films near the magnetic compensation temperature, which can be a consequence of both the spin-flop transition and the chemical composition gradient. In the work, an assessment of the possible chemical inhomogeneity of the films based on magnetic measurements was carried out and its relationship with the thickness of the samples was observed. Keywords: amorphous magnetic films, perpendicular magnetic anisotropy, ferrimagnetism, magnetic domain structure, magnetic hysteresis.

Systematic data on the structural state and magnetic properties of films belonging to the binary Dy 100 – x Co x system have been measured within broad ranges of compositions (0 ≤ x < 85), temperatures (5‒300 K), and magnetic fields (0–70 kOe). It was found that in the absence of magnetic moment on Co atoms ( x ≤ 50), the films are in an asperomagnetic state, in which a considerable and nonmonotonical concentration change in the principal magnetic characteristics is observed. In the region of x > 50, the films have a sperimagnetic structure. It has been shown that the quantitative description of spontaneous magnetization in such a state can be obtained in the molecular field model.

The effect of an ultrathin Ti spacer on the exchange bias in Fe10Ni90/Ti/(Gd-Co) and Fe10Ni90/Ti/(Dy-Co) multilayers was investigated. It is shown that a change in the thickness of the spacer can lead not only to a change in the value of the exchange bias field, but also to a change in the features of magnetization reversal of the interacting layers. With a spacer thickness of from 0 to 0.7 nm in all considered film systems, a strong interlayer coupling takes place, which manifests itself in the joint magnetization reversal of the ferromagnetic (Fe-Ni) and ferrimagnetic (Gd-Co or Dy-Co) layers. In the samples with thicker Ti spacers, the joint magnetization reversal of the layers does not occur, but an exchange bias of the minor hysteresis loops for the ferromagnetic layer is observed, which also indicates the presence of an interlayer exchange interaction. An increase in the thickness of the spacer up to 1 nm for Fe10Ni90/Ti/(Gd-Co) films and up to 1.2 nm for Fe10Ni90/Ti/(Dy-Co) films disrupts the exchange coupling between the corresponding layers.

The magnetic properties of the Dy-Co binary system thin films were studied. The compositional dependences of the residual magnetization, the coercivity in the ground state, and the magnetic ordering temperature were determined. The intervals of the compositions corresponding to the asperomagnetic and sperimagnetic structures are established. Within these structures, the dependence of the average magnetic moment per Dy atom was calculated, and the fan of the Dy magnetic moments was concluded to be narrowed monotonously with increasing Co content in the range of 20-80 at.%.