Magnetocrystalline anisotropy in a (110) (Tb0.27Dy0.73)Fe2 thin-film

Magnetic anisotropy measurements performed in a (110) (Tb0.27Dy0.73)Fe-2 (Terfenol-D) film epitaxially grown on a sapphire substrate are presented. The magnetic torque curves have been determined by using a vectorial vibrating sample magnetometer, which allows us to measure the angular dependence of magnetization components parallel, M-\\, and perpendicular, M-perpendicular to, to the applied field up to 2 T. The fourfold symmetry associated with the cubic structure within the (110) plane is clearly observed. The analysis of the experimental torque has been carried out considering magnetocrystalline anisotropy up to sixth order and magnetoelastic energy up to second order; so, the magnetocrystalline anisotropy constants in the (110) plane of the film, K-1 and K-2, have been obtained. This allows us to determine the direction of the magnetization easy axis for (110) Terfenol-D thin-film: it is [112] at RT, passes through [334] at 140 K and then changes to [120] at 40 K. It was completely impossible to explain the angular dependence of the experimental magnetic torque without including shear and tetragonal magnetoelastic stress parameters, b(2) and b(1), respectively. This confirms the paramount role of the strain in the determination of the magnetic properties in this kind of Terfenol-D thin film.