Second- and fourth-order anisotropy constants near the spin reorientation transition in Co/Ho thin films
Institut de Physique et Chimie des Matériaux de Strasbourg,
23 rue du Loess, 67037 Strasbourg, France
2 Institut fur Experimentalphysik, Freie Universitat Berlin, Arnimallee 14, D-14195 Berlin, Germany
Accepted: 15 July 1997
Epitaxial buried Co/Ho films have been studied ex situ by means of polar magneto-optical Kerr effect and X-ray magnetic circular dichroism (XMCD) at the rare-earth edge. The very weakly polarized Ho overlayer strongly enhances the perpendicular magnetic anisotropy of the Co layer and leads to a temperature-induced Spin Reorientation Transition (SRT). From a quantitative evaluation of the second- and fourth-order constants K2eff, K4 of the magnetic uniaxial anisotropy as a function of temperature, it is shown that the continuous SRT results from the different thermal variations of these anisotropy constants, assuming a coherent rotation of the magnetization: K2eff varies quasi-linearly with the temperature and changes sign near the SRT temperature, whereas K4 is positive and nearly temperature-independent.
PACS: 75.30.Gw – Magnetic anisotropy / 75.70.-i – Magnetic films and multilayers
© EDP Sciences, 1997