FMR STUDY OF MBE-GROWN CO FILMS ON AL2O3 AND MGO SUBSTRATES

FMR studies of epitaxial Co(0001) films on Al2O3(112BAR0) and Co(112BA R0) on MgO(001) substrates have been performed at the X-band and in th e temperature range 80-400 K. For the samples on sapphire substrates t he resonance field behavior as a function of the dc magnetic field ori entation in the plane of the film exhibits a uniaxial anisotropy. In c ontrast, for the Co films on MgO substrates a fourfold anisotropy in t he film plane has been observed. Both in-plane anisotropies are unexpe cted with regard to the Co film structure. The FMR analysis shows that the fourfold anisotropy for Co/MgO occurs due to a twinned film struc ture consisting of two Co domains with their c-axes in the film plane and perpendicular to each other.