Magnetostriction of TbDy single crystals under compressive stress

Linear magnetostriction, magnetization, and Young´s modulus were measured in a b-axis single-crystal rod of Tb_0.5Dy _0.5. Huge magnetostrictions reaching 0.5-0.6% in fields of 2000 Oe were observed at 77 K. Three magnetization regions can be distinguished: (1) a low field region where the magnetization process is dominated by moment rotation; (2) a region where the magnetization jumps from one easy direction (a-axis) to another closer to the applied field direction; and (3) a slow approach to saturation as the applied field pulls the magnetization into the hard b-axis direction. The crossover from one region to another is determined by the applied stress and the demagnetization factor. A simple theory explaining each process is presented