Continuous structural phase transition and antiferromagnetic order in ilmenite-type NiVO

山本 孟*; 池田 理*; 本田 孝志*; 木村 健太*; 青山 拓也*; 大串 研也*; 鈴木 昭夫*; 石井 賢司*; 松村 大樹   ; 辻 卓也  ; 小林 慎太郎*; 河口 彰吾*; d'Astuto, M*; 虻川 匡司*

Yamamoto, Hajime*; Ikeda, Osamu*; Honda, Takashi*; Kimura, Kenta*; Aoyama, Takuya*; Ogushi, Kenya*; Suzuki, Akio*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; Kobayashi, Shintaro*; Kawaguchi, Shogo*; d'Astuto, M.*; Abukawa, Tadashi*

We investigate the crystal and electronic structures as well as magnetic properties of ilmenite-type NiVO, which has attracted research interest as an = 1 honeycomb lattice magnet. Ilmenite-type NiVO samples were synthesized under high-pressure and high-temperature conditions. Synchrotron X-ray diffraction and Rietveld refinement results demonstrated that NiVO underwent a continuous structural phase transition from the triclinic () phase to the rhombohedral () phase at 450 K. This transition is concomitant with the decomposition of the V-V dimers formed by the tetravalent V ions. X-ray absorption spectroscopy measurements confirmed that the Ni and V ions were divalent and tetravalent, respectively. Magnetic and specific heat measurements revealed that NiVO underwent an antiferromagnetic transition at 140 K, and a zigzag-type magnetic order with magnetic propagation vector =(0,1/2,0) was observed by neutron diffraction measurements.