Direct evidence of magnetization rotation at the ferromagnetic morphotropic phase boundary in Tb1-xDyxFe2 system

The large magnetostriction at the ferromagnetic morphotropic phase boundary (MPB) relies on easy magnetization switching under external magnetic fields. It has been proposed that both domain wall motion and magnetization rotation occur under external magnetic fields at the ferromagnetic MPB. However, direct experimental evidence of the latter is still lacking. Here we report direct evidence of both magnetization rotation and domain wall motion under an external magnetic field at the MPB of the Tb1-xDyxFe2 system through in situ synchrotron x-ray diffraction experiments, which are further confirmed by phase field simulations. This work unravels the origin of the large magnetostriction at the ferromagnetic MPB and could shed light on the design of magnetostrictive materials.