Magnetostriction-jump effect in <110> oriented Tb_0.3Dy_0.7Fe_1.95 crystal after non-coaxial field annealing

An <110> oriented Tb_0.3Dy_0.7Fe_1.95 rod was annealed under a field of 0.3 T, which was applied 35° away from its axis. Magnetostriction-jump effect of the magnetically annealed crystal was investigated under a series of uniaxial compressive pre-stresses ranging from 0 to 30 MPa. The magnetically annealed crystal possessed much higher saturation magnetostriction λ_s than the ones without applying any pre-stresses. When the compressive pre-stress was less than 20 MPa, the magnetically annealed specimen still exhibited obvious magnetostriction jump effect, possessing improved saturation magnetostriction λ_s and enhanced burst magnetostriction λ_m. A satisfactory magnetostriction as high as 2315 × 10^-6 could be obtained in the annealed crystal with the application of a pre-stress of 20 MPa. Furthermore, under a compressive pre-stress below 5 MPa, the critical field at which the magnetostriction-jump effect occurs also decreased, which was beneficial for low field applications. Difference in the magnetization processes caused by magnetic annealing was revealed through investigating the pre-stress dependences of the burst field H_jump and the distribution width of non-180° domain wall motion. Magnetic force microscopy images showed the changes of magnetic domain configurations induced by field annealing. Effects of the induced additional anisotropy on the magnetostrictive behaviors were also discussed.