A. V. Svalov

Magnetism of Co layers in a Co/Si multilayer film

The magnetic properties of Co/Si multilayer films produced through rf ion sputtering were studied in the temperature range 4.2–300 K. The dependences of the spontaneous magnetization and hysteresis characteristics of the films on the thicknesses of the magnetic layers and nonmagnetic spacers are established. It is shown that these dependences are determined to a large extent by interlayer interfaces, in which the effective magnetic moment of the Co atoms and the exchange interaction decrease and magnetic-anisotropy dispersion arises. A probable cause of the interface formation is interlayer mixing (which is estimated to penetrate to a depth of 15 Å) and the strong effect of Si on the Co electronic structure.

Structure and magnetic properties of nanocrystalline FeCuNbSiB alloys after a thermomechanical treatment

The peculiarities of the formation of a nanocrystalline structure and induced magnetic anisotropy have been studied in Fe87−xCu1Nb3SixB9 alloys (x = 0, 4, 6, 8, 9.5, 11, 13.5 at. %) after thermomechanical treatment. Differences in the dynamics of the process of phase separation in the initial amorphous state, final phase composition, and magnitude and sign of induced magnetic anisotropy have been revealed depending on the initial content of silicon.

Spin-glass-like behavior of low field magnetisation in multilayer (Gd/Si/Co/Si)n films

Abstract The results of experimental investigations of magnetic properties of multilayer (Gd/Si/Co/Si) n films in low magnetic fields are represented. The spin-glass-like behavior of magnetization is found. The role of biquadratic exchange coupling in a forming of magnetic state of system is discussed.

Spontaneous magnetization and characteristics of temperature-induced magnetization of planar Co∕Si nanostructures

The magnetic properties of planar Co∕Si nanostructures with different nominal thicknesses of the magnetic (2–42nm) and nonmagnetic (0.3–10nm) constituent layers are studied in the temperature range 4.2–300K. It is established that in the presence of Si layers the spontaneous magnetization of Co decreases and its temperature dependence changes, and magnetic hysteresis is modified. The interlayer influence is interpreted as being due to the diffusion of Si into the Co layers, which results in the formation of magnetically disordered boundary interfaces with low average magnetization. The depth of the interfaces depends on the nominal thickness of the Si layers and is estimated to reach 1.6nm. A qualitative explanation of the characteristics of the magnetization of the experimental objects under the influence of a magnetic field and temperature is given in a model where the interfaces have a granular microstructure. Electron-microscope observations confirm some assumptions of the proposed model.

Magnetic compensation state peculiarities in [Gd-Co/X]n layered films

Sputtered multilayer [Gd-Co/X]n, (X = Cu, Ti, TiN, SiO2) films have been studied. The dependence of the compensation temperature on the material of protective layers for single layer Gd-Co films and extended temperature interval of the magnetic-compensation state for multilayer [Gd-Co/X]n films have been found. The connection of these peculiarities with the particularities of the structural and chemical state of Gd-Co films is discussed.

Magnetic hysteresis of Co/Si multilayers with variable thickness parameters

The magnetic properties of Co/Si multilayers with different thicknesses of Co (2–42 nm) and Si (0.3–10 nm) layers produced by high-frequency ion sputtering have been studied. Peculiarities of the microstructure of multilayered films and regularities of their magnetization with varying the magnetic field (0–500 Oe) and temperature (4.2–300 K) have been determined. A conception of the partial interlayer mixing with the formation of surface interfaces with a granular magnetic structure has been used for a model description of the structural and chemical states and magnetic properties of the multilayers. The relative volume of interfaces and parameters of their elements—granules—vary depending on the nominal magnitudes and relationship between the layer thicknesses. This leads to specific hysteretic effects. The interlayer interaction of domain walls is likely to play a certain role in the formation of the hysteretic properties.

Interlayer coupling and magnetization process in Co/X/Gd-Co (X = Si, Ti, Cu) artificial ferrimagnets

Multilayer Co/X/Gd-Co (X = Si, Ti, Cu) films have been prepared to study the exchange coupling between magnetic layers. A field-induced magnetic-phase transition from the collinear to noncollinear state was observed. The dependences of the transition field on the thickness of magnetic layers and nonmagnetic spacers have been found. The temperature dependence of the Gd-Co layer magnetization and the dependence of the transition field on the magnetic-layer thickness have been calculated in terms of the molecular-field theory.

Structural and Magnetic Phase Transformations in Multilayer Gadolinium Films

A study was made of the effect of thickness and thermal treatment on the microstructure and magnetic properties of Gd/Cu and Gd/Si multilayer films obtained by rf ion sputtering. It was found that the magnetic layers have an amorphous-crystalline structure, with the component ratio depending on the thickness of the magnetic layers and nonmagnetic spacers and on the annealing temperature. An analysis of the temperature dependences of the torque, which was made within the molecular field approximation, yielded a quantitative description of the changes in the film phase composition. The correlation between the exchange coupling parameter and the structural state of gadolinium was established.

Magnetic resonance in multilayer Gd/Si/Co magnetic films

The magnetic properties of multilayer Gd/Si/Co magnetic films are experimentally studied by electron magnetic resonance and analyzed theoretically. The introduction of a semiconductor silicon interlayer is found to substantially affect the magnetic interlayer coupling and the magnetic dynamics of the system. The interlayer coupling is shown to be ferromagnetic for the (Gd/Si)n films and to be antiferromagnetic for the (Gd/Si/Co/Si)n films. The temperature dependences of the exchange parameters and the gyromagnetic ratios are determined. Possible mechanisms responsible for the formation of the interlayer coupling are discussed.

Influence of magnetic field on the interlayer interaction in (Co/Si/Gd/Si)n films

A singularity sensitive to the external magnetic field was observed in the temperature dependences of the magnetization of multilayer (Co/Si/Gd/Si)20 films in the vicinity of compensation temperature. Possible mechanisms responsible for the unusual behavior of the magnetization are discussed.