Effects of magnetic flux densities and directions on domain structure and magnetostriction of 〈111〉-oriented Tb-Dy-Fe alloys during annealing in high magnetic fields

The directionally solidified (Tb_0.27Dy_0.73)_1.06Fe_1.95 alloys with 〈111〉-preferred orientation were annealed without and with various magnetic fields. Different initial domain structures were obtained via changing magnetic field directions and flux densities during annealing. The changes in microstructures, crystal orientation, domain evolution, and magnetic properties were investigated. The alloys annealed with parallel fields had higher magnetostriction in low-field ranges than those with vertical fields and without fields. Remarkably, the magnetostriction of alloys annealed with a 6 T parallel field reached 1034.6 ppm at 1000 Oe, increased by 110.2% compared to alloys annealed without fields. The magnetostrictive properties were regulated via changing the initial domain structure (i.e., magnetic moment orientation and domain width), rather than microstructures or crystal orientation after annealing in high magnetic fields. The orientation of domain moments was induced to align along the applied fields due to the relatively weak magnetic crystal anisotropy. The strip domain width increased with magnetic flux densities due to additional energy that drives the formation of larger domains. Research indicated that the magnetic moment orientation was the main factor for various magnetostriction. Thus, a model based on the rotation of domain moments between Easy Magnetization Directions was proposed to explain the changes in magnetostriction and magnetic property.