Phase field simulation of grain size effects on the phase coexistence and magnetostrictive behavior near the ferromagnetic morphotropic phase boundary

The grain size effects on the phase coexistence and magnetostrictive response of Tb_1-xDy_xFe₂ polycrystals near the ferromagnetic morphotropic phase boundary (MPB) are revealed through phase-field modeling. It shows that phase coexistence is a universal phenomenon in polycrystals for both ferromagnetic and ferroelectric MPB and that the range of compositions for phase coexistence increases with decreasing grain sizes. A large, reversible, and anhysteretic magnetostrictive response at low external fields is also found in the fine-grained polycrystals around the ferromagnetic MPB, which offers us a route to developing nanocrystalline magnetostrictive materials.