R. Zuberek

Magnetic field-induced spin reorientation in gadolinium surface layer of Gd/Fe multilayers

Magnetization processes in thin Gd/Fe multilayer films have been studied by means of the longitudinal magneto-optical Kerr effect and magnetization measurements. Comparison between magneto-optical and magnetic measurements allows one to conclude that a field-induced surface spin reorientation occurs in the studied films for a magnetic field applied in the film plane. The experimental results can be satisfactorily interpreted in the framework of the developed theoretical model. This model predicts a formation of a noncollinear magnetic structure within the gadolinium surface layer during the process of the field-induced spin reorientation phase transition.

Interface magnetostriction of sputtered Fe/C multilayers

Abstract The results of magnetostriction constant λ s of multilayer Fe/C sputtered films are reported. The measurements have been performed at room temperature using strain modulated ferromagnetic resonance method. The structure of films is amorphous, mixture of amorphous and cubic and purely cubic. The magnetostriction constant λ s is different for any phases and depends linearly on the inverse of the Fe layer thickness.

Magnetostriction of sputtered Co/C multilayers

Abstract The measurements of magnetostriction constant λs of Co/C multilayers have been performed at room temperature using strain modulated ferromagnetic resonance. The dependence of λs on the inverse Co layer thickness is interpreted as arising due to the volume and interface interactions. It is suggested that magnetostriction in Co/C systems arises mainly from dipole-dipole interaction.

Temperature and field dependence of magnetostriction in amorphous thin films

Abstract The theory of temperature and magnetic field dependence of magnetostriction in amorphous thin films has been developed for the following models: pair-ordering model, random anisotropy model and columnar structure model. Detailed calculations have been performed within the molecular field approximation and spin-wave approximation.

Orientation and layer thickness dependence on the longitudinal magnetization and transverse magnetization hysteresis loops of sputtered multilayer Fe/Si and Fe/Ge thin films

The transverse magnetization and longitudinal magnetization hysteresis loops of sputtered thin films of Fe/Ge and Fe/Si multilayers on GaAs(001) substrates have been studied. The dependence of the film magnetic anisotropy on the bilayer period and semiconductor composition was investigated using a MOKE magnetometer. The hysteresis loops were measured as a function of the angle between the applied magnetic field and the hard–hard axis of the film. For the longitudinal magnetization, the Fe/Si film loops had lower remanent magnetization compared to the Fe/Ge film with the same spacer thickness. Thus the Fe/Si film had stronger exchange coupling across the spacer layer compared to the Fe/Ge film. For the thicker Ge spacer layer film, no exchange coupling was measured. For the transverse magnetization, the Fe/Ge multilayer films loops had only one Barkhausen jump. For the Fe/Si multilayer films loops, some contained one Barkhausen jump while others had two jumps, due to the cubic anisotropy contribution. These results are interpreted in terms of anisotropy and exchange energies.

Formation of noncollinear spin configurations during magnetization reversal in multilayered Fe/Si films

Abstract Magnetization reversal processes in Fe/Si multilayered films have been studied by means of the longitudinal magneto-optical Kerr effect at room temperature. The multilayers have been grown by DC sputtering on the single-crystal GaAs substrate. The Kerr effect curves had areas with an invariable or slightly varying rotation and had different remanent rotation value in the zero magnetic field for different directions of the magnetic field in the film plane. The observed features are related to the formation of stable and metastable noncollinear spin configurations. The experimental results are explained in the framework of the theory, which takes into account the competition between the bilinear exchange term on the one hand and the biquadratic exchange or cubic magnetic anisotropy terms on the other hand.

Magnetooptical studies of the H–T phase diagram of an Fe/Si multilayered film

The magnetization reversal of a multilayered Fe/Si film having cubic magnetocrystalline anisotropy is investigated in the temperature interval 25–300 K by magnetooptical methods. It is found that the growth of the biquadratic exchange interaction as the temperature is lowered causes a spontaneous second-order phase transition from a collinear antiferromagnetic state to a noncollinear state. The presence of cubic anisotropy in the film gives rise to spontaneous and magnetic-field-induced first-order phase transitions between noncollinear states. Magnetooptical studies permit constructing the H–T magnetic phase diagram of the multilayered Fe/Si film for an orientation of the external field along the hard magnetization axis [110]. A calculation of the H–T phase diagram in the framework of a model taking into account the bilinear exchange and cubic anisotropy, with constants I1 and K that are assumed to be independent of temperature, and also the biquadratic exchange with a linearly temperature-dependent cons...

Noncollinear magnetic structures in an Fe/Si/Fe film with a ferromagnetic interlayer exchange interaction

Results are presented from magnetic and magnetooptical studies of the magnetic configurations in a three-layer film Fe(30 A)/Si(14 A)/Fe(30 A) in which ferromagnetic and biquadratic exchange between iron layers is observed and which also possesses cubic and uniaxial anisotropy. These studies were done at temperatures of 300 and 10 K. It was found that in the absence of magnetic field a noncollinear magnetic structure, the form of which changes with temperature, is observed in this system. A calculation of the stable noncollinear configurations is done on the basis of a model in which it is assumed that both the exchange interaction constant and the cubic and uniaxial anisotropy constants in the iron layer change with temperature. The values of the angles characterizing the magnetization direction in the iron layers in the stable noncollinear configurations are determined on the basis of a comparative analysis of the experimental data and the results of the calculation. It is shown that both the angle betw...

The influence of nitrogen on the structural and magnetic properties of nanocrystallized Finemet-type ribbons

Abstract Nitriding thermochemical treatment under suitable parameters, used to nanocrystallize Fe–Cu–Nb–Si–B ribbons, leads to finer grain size and modifies the structural parameters of the α-Fe(Si) phase: low Si content, probably due to the formation of Si–N precipitates on a very fine scale. Furthermore, both the specific magnetization of the alloy and the Curie temperature of the crystalline phase increase upon nitrogenation and the magnetostriction decreases in relation with the higher crystalline volume fraction. It is shown that nitrogenation offers a new method to obtain nanostructured materials.

Low temperature enhancement of the magnetic anisotropy in Fe/Si multilayers

The FMR and SQUID investigation of the magnetic anisotropy of Fe/Si multilayers are presented. The multilayers, with various thicknesses of iron and a thick layer of silicon (in order to eliminate the coupling between Fe layers), have been grown by DC sputtering on single crystal GaAs substrates. Low temperature enhancement of the easy-plane anisotropy, especially below 50 K, was observed. This anisotropy seems to be of magnetoelastic origin. The coercivity was shown to decrease with temperature.