Chemical substitution-induced ferroelectric polarization rotation in BiFeO3.

and multiferroic [ 2 ] materials. For instance, ferroelectric materials at morphotropic phase boundaries (MPB), where multiple structural phases with ferroelectric polarizations pointing in different crystallographic directions coexist, often display large piezoelectric coeffi cients. [ 3– 5 ] It is the ferroelectric distortions, which accompany the polarization rotation that leads to enhancements in the piezoelectric coeffi cient. In multiferroic BiFeO 3 (BFO), it has been shown [ 2 ] that the coupled antiferromagnetic order can be altered by switching the ferroelectric polarization vector. In fact, the ability of a material to display polarization rotation is recognized as an important precursor to occurrence of an MPB. [ 5 , 6 ]