V–V Dimerization and Magnetic State of Cobalt Ions in Ilmenite-Type CoVO₃

Abstract

The nature of chemical bonds determines the electronic and magnetic properties of compounds. A metal–metal bonding (V–V dimer) and its effect on the magnetism of ilmenite-type CoVO3 were studied. Polycrystalline CoVO3 samples were synthesized using a high-pressure synthesis method. Crystal structure refinement revealed that V–V dimers exist at temperatures below 550 K in the vanadium layers. Co2+ in CoVO3 exhibits an S = 3/2 state, whereas a J eff = 1/2 state was reported in ilmenite-type CoTiO3. The existence of V–V dimers reduces the structural symmetry (from R to P ), which can change the magnetic ground state.

High-pressure ilmenite-type MnVO3: crystal and spin structures in the itinerant-localized regimes

“…MgVO 3 , with a V–V dimer distance of ∼2.78 Å, shows a non-magnetic nature due to the 3d xy orbital pairing below 500 K. 10 CoVO 3 , with a ∼2.74 Å V–V distance, presents dimerized vanadium and is considered to be magnetic solely due to cobalt cations with a S = 3/2 state. 11 MnVO 3 -I has a ∼2.85 Å V–V dimer bond, also below the critical distance for direct exchange ( R c ∼ 2.94 Å). 30,31 Along with the metal-like – semiconductor transition observed at 450 K, it is thus expected, by analogy, to be magnetic exclusively due to the manganese cations.…”

“…7–9 MgVO 3 and CoVO 3 exhibit a ladder-like V–V dimerization and non-magnetic singlet ground states with a concomitant triclinic to rhombohedral phase transformations at 500 and 550 K respectively. 10,11 NiVO 3 and CuVO 3 have not been fully studied. 9,12,13…”

Single Crystal Growth of Ilmenite-Type MnVO3 by Solid-State Recrystallization

“…This compound shows a triclinic distortion at room temperature, but the crystal structure has not been refined thus far. We have previously studied other ilmenite-type vanadates, including MgVO 3 and CoVO 3 . , These compounds also show triclinic distortions. This distortion originates from the direct chemical bonding between adjacent vanadium ions, which results in the formation of V–V dimers.…”

Role of V–V dimerization on electronic and magnetic properties of ilmenite-type CoVO3

“…twodimensional honeycomb framework formed by edge-shared CoO 6 octahedra and Co 2+ electronic configuration, as alluded above. More recently, ilmenite-type CoVO 3 was synthesized via high-pressure synthesis approach, and magnetic susceptibility measurement indicated that an AFM transition takes place at 140 K [5,6], with the Co 2+ ions being the S = 3/2 state, offering another platform to highlight the essential magnetic interactions in the search for quantum spin liquid state.…”

“…One of the most distinctive features in ilmenite-type vanadates, is the formation V-V dimerization, initiating a structure transition from high temperature rhombohedral phase to low-temperature triclinic one (P 1). Actually, CoVO 3 exhibits a phase transition from R 3 to P 1 at 550 K [5,6]. V-V dimers are present in low-temperature phase, arranged in a ladder-like pattern, analogues to MgVO 3 [7].…”