V. O. Vas’kovskii

Multilevel interaction between layers in layered film structures

An analysis was carried out of the mechanism underlying magnetic interlayer interaction in film structures. The investigation was based on the assumption that interlayer bonding affects film hysteresis. This was based on experimental data on the coercive force, the domain structure parameters, and the microstructure of Fe19Ni81/Cr/Fe19Ni81 and Fe15Co20Ni65/Cr/Fe15Co20Ni65 films. Theoretical estimates show that, as the thickness of the Cr interlayer increases, the exchange interaction between the ferromagnetic layers can be replaced by the magnetostatic interaction whose effectiveness is determined by surface irregularities and layer ‘magnetization ripples’.

Magnetoresistive Fe19Ni81/Tb-Co medium with an internal magnetic bias

The magnetization reversal and magnetoresistance of two-layer exchange-coupled Fe19Ni81/Tb-Co films are studied. Amorphous TbxCo100 − x layers with 30 < x < 35 are found to have a uniaxial magnetic anisotropy and a rather high coercive force, which ensures magnetic biasing of the adjacent permalloy layers. In addition, the permalloy layers subjected to selective annealing exhibit a significant anisotropic magnetoresistance and a small magnetic hysteresis. These properties make it possible to consider the developed film structure as an effective magnetoresistive medium. This structure is used to form magnetic sensor samples that have an odd transfer function in the absence of external magnetic biasing.

Chapter 9 Magnetism of multilayer films in transition metal/semiconductor system

In this paper, we present the current status of experimental research in the field of magnetism in multilayer films based on a transition metal/semiconductor system. Exchange interactions are analyzed depending on the technology of film fabrication, materials of different layers, thicknesses of magnetic and non-magnetic layers, temperature, magnetic field, and optical radiation.

Regularities in Penetration of Electromagnetic Waves through Metallic Magnetic Films

Penetration of millimeter electromagnetic waves through permalloy films under magnetic resonance conditions is studied experimentally and theoretically. Measurements are taken on film samples from 40 to 200 nm in thickness in a frequency range from 26 to 38 GHz. Magnetic resonance, antiresonance, and spin-wave resonance are observed. The resonance spectrum is reconstructed. The Gilbert damping constant is determined for a series of films. It is shown that the damping constant decreases upon an increase in the film thickness. The resonance line profile is calculated, and the dependences of resonance line amplitude and width on experimental conditions and material parameters of the film are determined.

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.