CoVO3 High‐Pressure Polymorphs: To Order or Not to Order?

Materials properties are determined by their compositions and structures. In ABO3 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, CoVO3 obtained in both ilmenite‐(CoVO3‐I) and LiNbO3‐type (CoVO3‐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 CoVO3‐II shows a cluster‐glass behavior while CoVO3‐I hosts a honeycomb zigzag magnetic structure in the cobalt network. First principles calculations show that the influence of vanadium is crucial for CoVO3‐I, although it is previously considered as non‐magnetic in a dimerized spin‐singlet state. Contrarily, CoVO3‐II shows two independent interpenetrating antiferromagnetic Co‐ and ferromagnetic V‐hcp sublattices, which intrinsically frustrate any possible magnetic order. CoVO3‐II is also remarkable as the first oxide crystallizing with the LiNbO3‐type structure where both metals contain free d electrons. CoVO3 polymorphs pinpoint therefore as well to a much broader phase field of high‐pressure A‐site Cobaltites. Here, the unique diversity of magnetic behavior in two polymorphs of CoVO3 is reported. (I) shows a close relation to Kitaev honeycomb magnets with the zigzag‐type magnetic structure and its origin is elucidated using first‐principle calculations. (II) crystallizes in a LiNbO3‐type structure and presents a cluster spin glass driven by a novel mechanism of magnetic frustration from interpenetrating antiferromagnetic and ferromagnetic sublattices.