The rise of a new subfamily of perovskite materials A2A’A’’B4O12 with intrinsic triple A-site ordering
Seminar Hall 31, 2nd Floor, Main Building
Abstract:
A-site ordered quadruple perovskites, AA’3B4O12, show many interesting physical and chemical properties, for example, inter-site charge transfer and disproportionation, giant dielectric constant, multiferroic properties, and an electric dipole helical texture. These discoveries have led to a considerable research effort to synthesize and characterize such quadruple perovskites. AA’3B4O12 has a 12-fold-coordinated A site and a square-planar-coordinated A’ site, while B sites have a usual octahedral coordination for perovskites. The AA’3B4O12 subfamily of the perovskite family has numerous representatives.
In the last years, we explored another special class of perovskite materials with the general composition of A2A’A’’B4O12. They are called A-site columnar-ordered quadruple perovskites, where A’ is a site with a square-planar coordination and A’’ is a site with a tetrahedral coordination. The presence of 3d-5d transition metals at three sites – A’, A’’, and B – with original columnar-type arrangements of A cations can lead to new functionalizes because of unusual exchange pathways not seen in other perovskites.
In this talk, I will introduce such A2A’A’’B4O12 perovskites and their design ideals. Then, I will present a few examples, when we can manipulate with their properties through compositions. In particular, I will present results on Y2A’A’’Mn4O12. Depending on the composition at the A’ and A’’ sites different magnetic ground states and a different number of magnetic transitions are realized: Y2MnMnMn4O12 (with reduced ordered moments and competitions between antiferromagnetic and ferrimagnetic ground states), Y2MnGaMn4O12 (with spin-glass magnetic properties), Y2CuMnMn4O12 (with three ferrimagnetic transitions at 175, 115, and 17 K), Y2CuGaMn4O12 (with one ferrimagnetic transition at 115 K), and Y2CuZnMn4O12 (with two transitions at 115 K and 30 K).