Fe-Tb alloy films prepared by ion beam-assisted deposition

Fe-Tb multilayers and alloy films prepared by sputtering or evaporation are found to have perpendicular magnetic anisotropy. In this work, Fe-Tb alloy films with parallel magnetic anisotropy in a wide composition range, 3-30 at.% Tb, are obtained for the first time, prepared by the ion beam-assisted deposition technique. All the films have an easy magnetization axis in the film plane. A supersaturated bcc solid solution phase with enlarged lattice and increased saturation magnetization is obtained in the range of 6.5-13 at.% Tb; while in the range of 21-30 at.% Tb, the films are amorphous and have lower saturation magnetization. Thermodynamic calculation of the Gibbs free energy of the Fe-Tb system shows that both the bcc solid solution and the amorphous phase are energetically and dynamically favoured in the two composition regions, respectively.