Anisotropy in Fe layers investigated by ferromagnetic resonance

摘要

Ferromagnetic resonance (FMR) is performed together with superconducting quantum interference device and Faraday magnetometry to investigate the magnetic anisotropy of epitaxial bcc Fe(001) films on Ag(001) and Cr(001). The Fe/Ag(001) and Fe/Cr(001) layers as well as corresponding wedge structures were grown by molecular-beam epitaxy. On these samples the following investigations were done. Firstly the temperature dependence of the surface anisotropy of the Fe/Ag system was determined. To achieve high precise values of the surface anisotropy a locally resolved FMR technique was applied to an Fe wedge film coated in Ag layers. Secondly the influence of strong deformation of the Fe layer on the magnetic properties was investigated by high-dose Fe-ion implantation in thermally immiscible Fe/Ag(001) layer structures. FMR measurements have shown a pronounced tetragonal symmetry of the anisotropy, which can be precisely controlled by implantation conditions. Thirdly in Fe/Cr single-crystal layers the magnetic parameters of the Fe films show an anomalous temperature behaviour for a distinct Cr thickness range that can be related to the spin-flip transition. The transition temperature decreases continuously with decreasing Cr thickness, ceasing in a suppression of the spin flip for Cr thicknesses below 60 Angstrom. Below the transition temperature an increase in the dynamic contribution to the FMR linewidth occurs which depends on the Cr thickness. The temperature variation in the dynamic line broadening is explained by a band theoretical description which agrees qualitatively with the temperature variation in the magnetic Fe moment. [References: 24]