Abstract
Materials properties are determined by their compositions and structures. In ABO(3) oxides different cation orderings lead to mainly perovskite- or corundum like derivatives with exciting physical properties. Sometimes, a material can be stabilized in more than one structural modification, providing a unique opportunity to explore structure-properties relationship. Here, CoVO(3) obtained in both ilmenite-(CoVO(3) -I) and LiNbO(3) -type (CoVO(3) -II) polymorphs at moderate (8-12 GPa) and high pressures (22 GPa), respectively are presented. Their distinctive cation distributions affect drastically the magnetic properties as CoVO(3) -II shows a cluster-glass behavior while CoVO(3) -I hosts a honeycomb zigzag magnetic structure in the cobalt network. First principles calculations show that the influence of vanadium is crucial for CoVO(3) -I, although it is previously considered as non-magnetic in a dimerized spin-singlet state. Contrarily, CoVO(3) -II shows two independent interpenetrating antiferromagnetic Co- and ferromagnetic V-hcp sublattices, which intrinsically frustrate any possible magnetic order. CoVO(3) -II is also remarkable as the first oxide crystallizing with the LiNbO(3) -type structure where both metals contain free d electrons. CoVO(3) polymorphs pinpoint therefore as well to a much broader phase field of high-pressure A-site Cobaltites.