Session 6-3

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 (Figure 1 (left)), 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 (Figure 1 (right)) [1]. 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 work, we 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) [2], Y₂MnGaMn₄O₁₂ (with spin-glass magnetic properties) [3], Y₂CuMnMn₄O₁₂ (with three ferrimagnetic transitions at 175, 115, and 17 K; among them: two spin-reorientation transitions at 115 and 17 K) [4], Y₂CuGaMn₄O₁₂ (with one ferrimagnetic transition at 115 K) [5], and Y₂CuZnMn₄O₁₂ (with a ferrimagnetic transition at 115 K and a spin-reorientation transition at 30 K). We will also discuss other levels of flexibility of such perovskites.