THE DOMAIN-STRUCTURE OF FERROELASTIC BIVO4 STUDIED BY MAGNETIC RESONANCES

The domain structure of the ferroelastic BiVO4 single crystal has been investigated using the nuclear magnetic resonance (NMR) of V-51 and b y the electron paramagnetic resonance (EPR) of the Mn2+ ions contained in the crystal as an impurity. The 14 resonance lines of V-51 (I = 7/ 2) in a BiVO4 Crystal with the twin domain were measured in the crysta llographic a-b (or c-b) and c-a (or a-c) planes with an FT NMR Spectro meter. Two sets of Mn2+ EPR signals were also obtained in the c-a plan e. These two sets Of NMR and EPR signals originate from the twin-domai n structure. From these two sets of experimental data from V-51 NMR an d Mn2+ EPR, it is confirmed that the BiVO4 single crystal has the prom inent (W-plane) domain wall reported previously. The investigated doma in structure is found to be stable with time in contrast with a previo us report by Baran et al. The previous model of the twinning mechanism derived from NMR and x-ray diffraction data has been improved by empl oying the EPR results. The observed W plane of the domain wall in BiVO 4 can be explained by the ferroelastic species 4/mmm F 2/m instead of 4/m F 2/m.