The domain structure of ferroelastic BiVO4 crystal studied by Gd3+ EPR

The domain structure of ferroelastic BiVO4 single crystal has been investigated using the electron paramagnetic resonance (EPR) of the Gd3+ ions existing as an impurity in the crystal. Two sets of Gd3+ EPR signals were obtained in the crystallographic ca-plane. These two sets of signals originated not from the two kinds of substitutional sites but from the twin-domain structure in the host crystal. It is found that the BiVO4 crystal investigated with Gd3+ EPR has the prominent (W-plane) domain wall. The domain structure is stable in contrast with a previous report by Baran et al. From the observed W-plane of the domain wall, it is suggested that a ferroelastic transition in BiVO4 is 4/mmm F 2/m instead of 4/m F 2/m. The model of twinning mechanism improved in a previous report by Mn2+ EPR is confirmed by Gd3+ EPR.