IMF2017

The elastic properties of uniaxial relaxor Ca_xBa_1-xNb₂O₆ (x = 0.30, CBN30) c-plate single crystals were studied under a dc electric field using broadband Brillouin scattering spectroscopy. Below the Curie temperature, T_C = 231 ^oC, a sizable change of the longitudinal acoustic (LA) velocity (v_LA) was observed near the coercive field when switching the electric field direction from [001] (+E) to [00-1] (-E). Internal random fields (RFs) restrict the growth into macrodomains by stabilizing the nanodomain state, while the external +E suppresses RFs and, as a result, a gradual increase of polarization was observed. After complete switching of polarization and just before the growth of nanodomain into a macrodomain state, +E was gradually removed and -E was applied. By increasing –E, a sharp increase of v_LA was observed which indicates a complete switching of the nanodomain into the macrodomain state with opposite polarity along -E. After removing –E and gradually reapplying +E, LA mode splitting was observed, which indicates a state consisting of coexisting macrodomains induced by -E and +E, respectively. The lower-frequency LA mode corresponds to the macrodomain state due to -E, while the higher-frequency LA mode corresponds to the macrodomain state due to +E. The v_LA of the macrodomain state induced by +E is higher than that of the macrodomain state induced by –E. This proves that the macrodomain state triggered by +E is more stable. Field cooling processes under +E and –E were also investigated.