Electric and magnetic transitions with 90° turning of polarizations in a layered perovskite of [NH4Cl]2[Ni(HCOO)2(NH3)2]

A hybrid layered perovskite compound of [NH4Cl]2[Ni(HCOO)2(NH3)2] consists of alternatively stacked perovskite layers of [Ni(HCOO)2(NH3)2] and CsCl-type slabs of [(NH3)2(NH4Cl)2]. The material undergoes a ferro- to ferro-electric transition around 110 K, from a high temperature, high polarized phase to a low temperature, low polarized one via an intermediate incommensurate phase and then a para- to antiferro-magnetic transition at 25 K. It displays significant anisotropic dielectric and magnetic responses, and both electric and magnetic polarizations turn from the direction perpendicular to the layers to the direction parallel to the layers during the transitions.