Magnetostriction of a <110> oriented Tb_0.3Dy _0.7Fe_1.95 polycrystals annealed under a noncoaxial magnetic field

A <110> oriented Tb_0.3Dy_0.7Fe_1.95 alloy rod was annealed at 500 °C under a magnetic field of 0.3 T, which was applied 35° away from the rod axis. X-ray diffraction characterization and optical microscopy observation showed that both the crystal orientation and morphologies were retained after magnetic annealing. Magnetic force microscopy images exhibited obvious change of the magnetic domain configurations. The magnetostrictive performance was changed drastically. Saturation axial magnetostriction λ||_s increased from 1023 to 1650 ppm by the ratio of 61.3%, but saturation perpendicular magnetostriction λ_s decreased from -802 to -624 ppm. Maximum magnetostrictive strain coefficients d₃₃ and d₃₁ were found to be enhanced by 29.3% and 32.6%, respectively. In addition, the fields for obtaining both optimum d₃₃ and d₃₁ decreased, which indicates that better magnetostrictive performance can be achieved at lower external fields after magnetic annealing.