Magnetic anisotropy in Gd/(FeCo) and Gd/Fe multilayers for high density magneto-optical recording

Very recently, new techniques in the magneto-optical recording were propose d which promise the readout of domains smaller than the optical diffraction limit. For this purpose Gd-(Fe,Co) alloy films are used, which change thei r magnetization direction with temperature. In this experimental study for the first time spin reorientation effects in multilayers of Gd/(FeCo) and G d/Fe were investigated with varying composition and periodicity. Both Gd/(F eCo) and Gd/Fe films show a compositional dependence of the anisotropy simi lar to a phase transition. An in-plane to perpendicular spin reorientation near the compensation temperature T-comp can be obtained in rare earth rich films for small periodicities lambda similar to 1.1 nm, but for increasing lambda the anisotropy change occurs at temperatures different from T-comp. The opposite effect, i.e., spin reorientation from perpendicular to in-pla ne, can be observed in transition metal rich Gd/(FeCo) multilayers but not in Gd/Fe multilayers. The anisotropy behavior and the reorientation effects are explained qualitatively within a new model. (C) 1999 American Institut e of Physics. [S0021-8979(99)33208-4].