Electric Field Effect on NQR in Ferroelectric Materials

Abstract

Abstract The electric field effect on NQR in ferroelectric materials, 93Nb in LiNbO3 and 14N in NaNO2 and SC(NH2)2 , has been investigated at 77 K. In these crystals with single domain, only the line shift due to the external electric field was observed. In the case of NaNO2 powder and a crystal with multi-domains, line broadening was observed in the external electric field. These phenomena can be explained with the fact that the direction of spontaneous polarization in a domain is related to the direction of the applied electric field. The rate of the NQR line-shift due to the electric field is remarkably smaller in mostly ionic crystals, such as LiNbO3 and NaNO2 , than in a molecular crystal such as SC(NH2)2 . This is due to the strong ionic bonding in ionic crystals. Also, the difference of the Stark shift'between NaNO2 and SC(NH2)2 is discussed in terms of the local electric field and polarizability at the resonant nuclear site.