Stereo-Active Lone-Pair Control on the Ferromagnetic Behavior in VO(SeO2OH)2: A New Acentric Ferromagnetic Material

摘要

A new acentric ferromagnetic material, VO(SeO2OH)2, has been synthesized and characterized by single crystal X-ray diffraction, second harmonic generation (SHG), and magnetization measurements. The crystal structure of VO(SeO2OH)2 consists of linear chains of corner-shared V~(4+)O6 octahedra that are connected by SeO2OH groups. The material exhibits a weak SHG efficiency, comparable to α-SiO2, and a ferromagnetic transition (T_C) at ~2.5 K with a saturated magnetic moment of 1.09 μ_B per formula unit (μ_B/FU). The origin of the ferromagnetism is explained by the suppression of the antiferromagnetic superexchange (SE) and supersuper-exchange (SSE) interactions in the infra-chain and inter-chain magnetic interactions, respectively. In addition, using first principles density functional theory (DFT) calculations, we show that the SSE interactions depend on the O(2)-Se~(4+)-O(3) angle. As we demonstrate, the stereoactive lone-pair on Se~(4+) is the driving force for the mrer-chain ferromagnetic interactions.