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.

具有反铁磁（antiferromagnetic, AFM）自旋轨道纠缠Jeff=1/2（基泰耶夫，Kitaev）相互作用的蜂窝状钴基体系，是量子磁学研究的目标体系。本文报道了两种高压（high pressure, HP）多型体CoVO₃-I（空间群P-1）与CoVO₃-II（空间群R3c），二者均具有堆叠蜂窝层结构，其反铁磁转变奈耳温度（Neel temperature, TN）分别为142 K与36 K。CoVO₃-I的有效磁矩（effective magnetic moment, μeff）=5.0(1)μ_B（玻尔磁子，Bohr magneton, μ_B）表明存在Co²+的自旋轨道耦合；而CoVO₃-II的有效磁矩μeff=4.4(1)μ_B则更接近V⁴+与Co²+的理论预期值4.24μ_B。解析这两种多型体的精确晶体与磁结构需借助中子衍射（neutron diffraction）技术，为此我们申请了WISH谱仪上2天的束流时间，用于在室温、奈耳温度以上以及低温基温下对小尺寸（50 mg）高压样品开展长程扫描数据采集。