Static and dynamic magnetic properties of a [Fe(35 Å)/Gd(50 Å)] superlattice are investigated experimentally in the temperature range 5-295 K using SQUID magnetometery and the ferromagnetic resonance (FMR) technique at frequencies 7-38 GHz. The obtained magnetization curves and FMR spectra are analysed theoretically using numerical simulation on the basis of the effective field model. At every given temperature, both static and resonance experimental data can be approximated well within the proposed model. However, a considerable temperature dependence of the effective field parameter in gadolinium layers has to be taken into account to achieve reasonable agreement with the experimental data in the entire temperature range studied. To describe the peculiarities of experimental FMR spectra, a non-local diffusion-type absorption term in Landau-Lifshitz equations is considered in addition to the Gilbert damping term. Possible reasons for the observed effects are discussed.

The effect of the chromium layer thickness on the magnetic state of an [Fe/Cr/Gd/Cr] n multilayer structure is studied. A series of Fe/Cr/Gd structures with Cr spacer thicknesses of 4-30 Å is studied by SQUID magnetometry and ferromagnetic resonance in the temperature range 4.2-300 K. The obtained experimental results are described in terms of an effective field model, which takes into account a biquadratic contribution to the interlayer coupling energy and a nonuniform magnetization distribution inside the gado linium layer (which was detected earlier). Depending on the magnetic field and temperature, the following types of magnetic ordering are identified at various chromium layer thicknesses: ferromagnetic, antiferro magnetic, and canted ordering. A comparison of the experimental and calculated curves allowed us to deter mine the dependence of the bilinear (J 1 ) and biquadratic (J 2 ) exchange constants on chromium layer thick ness t Cr . Weak oscillations at a period of about 18 Å are detected in the J 1 (t Cr ) dependence in the range 8-30 Å. The interlayer coupling oscillations in the system under study are assumed to be related to the RKKY exchange interaction mechanism via the conduction electrons of Cr.

Thin films of MnxSi1−x alloys with different Mn concentration x ≈ 0.44-0.63 grown by the pulsed-laser deposition (PLD) method onto the Al2O3 (0001) substrate were investigated in the temperature range 4-300 K using ferromagnetic resonance (FMR) measurements in the wide range of frequencies (f = 7-60 GHz) and magnetic fields (H = 0-30 kOe). For samples with x ≈ 0.52-0.55, FMR data show clear evidence of ferromagnetism (FM) with high Curie temperatures TC ∼ 300 K. These samples demonstrate the complex and unusual character of magnetic anisotropy described in the frame of phenomenological model as a combination of the essential second-order easy-plane anisotropy contribution and the additional fourth-order anisotropy contribution with the easy direction normal to the film plane. We explain the obtained results by a polycrystalline (mosaic) structure of the films caused by the film-substrate lattice mismatch.

A set of thin film Mn x Si 1−x alloy samples with different manganese concentration x ≈ 0.44 − 0.63 grown by the pulsed laser deposition (PLD) method onto the Al 2 O 3 (0001) substrate was investigated in the temperature range 4 − 300 K using ferromagnetic resonance (FMR) measurements in the wide range of frequencies ( f = 7 − 60 GHz) and magnetic fields (H = 0 − 30 kOe). For samples with x ≈ 0.52 − 0.55, FMR data show clear evidence of ferromagnetism with high Curie temperatures T C ∼ 300 K. These samples demonstrate complex and unusual character of magnetic anisotropy described in the frame of phenomenological model as a combination of the essential second order easy plane anisotropy contribution and the additional forth order uniaxial anisotropy contribution with easy direction normal to the film plane. We explain the obtained results by a polycrystalline (mosaic) structure of the films caused by the film-substrate lattice mismatch. The existence of extra strains at the crystallite boundaries leads to an essential inhomogeneous magnetic anisotropy in the film plane.