Ferroelectricity and structure in the YMnO(3) family.

The 1963 discovery of ferroelectricity in YMnO(3) was accompanied by an experimental Curie temperature (T(c)) reported as 913 K; this value was revised to 1270 K in the following decade. Subsequently, YInO(3) was shown to be isostructural with YMnO(3) and later demonstrated to satisfy the structural criteria for ferroelectricity; recent unpublished measurements give T(c) (YInO(3)) = 835 (15) K. The experimental T(c) value of 913 K for YMnO(3) is in satisfactory agreement with the calculated 1220 (100) K value as derived from a very recent structural refinement, the experimental T(c) of 835 (15) K for YInO(3) with the calculated 760 (120) K. The full YMnO(3) family includes the AMnO(3) subfamily with A = Y, Ho, Er, Tm, Yb, Lu, Sc, In; the AInO(3) subfamily with A = Y, Gd, Dy, Ho, Tb; and the AGaO(3) subfamily with A = Y, Ho, Er. The T(c) values of six family members with known structure, in addition to YMnO(3) and YInO(3), have been structurally derived as 1310 (110) K for ErMnO(3), 1290 (165) K for LuMnO(3), 1270 (110) K for YbMnO(3), 1220 (105) K for ScMnO(3), 540 (375) K for InMnO(3) and 1020 (100) K for YGaO(3). The agreement between predicted and experimental T(c) values for ErMnO(3), LuMnO(3) and YbMnO(3), in addition to that for YMnO(3) and YInO(3), leads to the confident prediction that ScMnO(3), InMnO(3) and YGaO(3) are new ferroelectrics. The remaining six members of the full YMnO(3) family are also expected to be new ferroelectrics.