Cation and spin ordering in CoVO3 high-pressure polymorphs.

Honeycomb cobalt-based systems with antiferromagnetic (AFM) spin-orbit entangled Jeff = 1/2 (Kitaev) interactions are desired for quantum magnetism research. Here, we present two high pressure (HP) polymorphs CoVO3-I (P-1) and CoVO3-II (R3c) with stacked honeycomb layers and AFM behaviour at TN = 142 and 36 K respectively. Effective magnetic moment μeff = 5.0(1) μB in CoVO3-I suggests the spin-orbit coupling of Co2+, while μeff = 4.4(1) μB in CoVO3-II is closer to the expected value of 4.24 μB for V4+ and Co2+. Neutron diffraction is essential to solve accurate crystal and magnetic structures for both polymorphs, for which 2 days of beamtime at WISH are requested to collect long scans at room temperature, above TN and at base temperature in small (50 mg) HP samples.