Magnetic anisotropy in (Tb_0.3Dy_0.7)₄₅Fe₅₅ amorphous films

Giant magnetostrictive (Tb_0.3Dy_0.7)₄₅Fe₅₅ thin films were prepared by direct current (DC) magnetron sputtering. The onset temperature of crystallization of the films is found to be 407°C through differential scanning calorimetery (DSC) studies. X-ray diffraction analysis confirms that the films exhibit an amorphous phase after annealing at 400°C. The effect of annealing on the in-plane anisotropy was investigated. The in-plane anisotropy is enhanced upon increasing the annealing temperature from 200°C to 400°C. The ratio M_r/M₁₀ is varied from 0.037 for the as-deposited sample to 0.543 after annealing at 400°C, where M_r and M₁₀ refer to remanence and magnetization measured at the field of 10kOe, respectively. In addition, pre-stress was also applied during deposition to induce an in-plane unidirectional anisotropy in the films. This may result in an anisotropy of the in-plane magnetization and lead to a large improvement of magnetostriction.