Ferroelectricity and structure in the YMnO3 family

The 1963 discovery of ferroelectricity in YMnO3 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, YInO3 was shown to be isostructural with YMnO3 and later demonstrated to satisfy the structural criteria for ferroelectricity; recent unpublished measurements give T-c (YInO3) = 835 (15) K. The experimental T-c. value of 913 K for YMnO3 is in satisfactory agreement with the calculated 1220 (100) K value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 YInO3 with the calculated 760 (120) K. The full YMnO3 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 YMnO3 and YInO3, have been structurally derived as 1310 (110) K for ErMnO3, 1290 (165) K for LuMnO3, 1270 (110) K for YbMnO3, 1220 (105) K for ScMnO3, 540 (375) K for InMnO3 and 1020 (100) K for YGaO3. The agreement between predicted and experimental T-c values for ErMnO3, LuMnO3 and YbMnO3, in addition to that for YMnO3 and YInO3, leads to the confident prediction that ScMnO3, InMnO3 and YGaO are new ferroelectrics. The remaining six members of the full YMnO3 family are also expected to be new ferroelectrics.