Observation of a Large Magnetic Anisotropy and a Field-Induced Magnetic State in SrCo(VO₄)(OH): A Structure with a Quasi One-Dimensional Magnetic Chain

Abstract

A new member of the descloizite family, a cobalt vanadate, SrCo­(VO4)­(OH), has been synthesized as large single crystals using high-temperature and high-pressure hydrothermal methods. SrCo­(VO4)­(OH) crystallizes in the orthorhombic crystal system in space group P212121 with the following unit cell parameters: a = 6.0157(2) Å, b = 7.645(2) Å, c = 9.291(3) Å, V = 427.29(2) Å3, and Z = 4. It contains one-dimensional Co–O–Co chains of edge-sharing CoO6 octahedra along the a-axis connected to each other via VO4 tetrahedra along the b-axis forming a three-dimensional structure. The magnetic susceptibility of SrCo­(VO4)­(OH) indicates an antiferromagnetic transition at 10 K as well as unusually large spin orbit coupling. Single-crystal magnetic measurements in all three main crystallographic directions displayed a significant anisotropy in both temperature- and field-dependent data. Single-crystal neutron diffraction at 4 K was used to characterize the magnetically ordered state. The Co2+ magnetic spins are arranged in a staggered configuration along the chain direction, with a canting angle that follows the tipping of the CoO6 octahedra. The net magnetization along the chain direction, resulting in ferromagnetic coupling of the a-axis spin components in each chain, is compensated by an antiferromagnetic interaction between nearest neighbor chains. A metamagnetic transition appears in the isothermal magnetization data at 2 K along the chain direction, which seems to correspond to a co-alignment of the spin directions of the nearest neighbor chain. We propose a phenomenological spin Hamiltonian that describes the canted spin configuration of the ground state and the metamagnetic transition in SrCo­(VO4)­(OH).

Field tunable magnetic transitions of CsCo2(MoO4)2(OH): a triangular chain structure with a frustrated geometry

“…This could be due to the significant orbital contribution since orbital moments are unquenched for Co 2+ in an octahedral environment (t 2g 5 e g 2 , S = 3/2, L = 3, gs = 4 T 1g ). Similar higher values have been noticed previously for pseudo-1-D Co 2+ compounds such as SrCo(VO 4 )(OH) (5.4m B per Co), 54 Na 4 CoTeO 6 (5.14m B per Co) 55 and NaCo 2 (SeO 3 ) 2 (OH) (4.84m B per Co). 25 However, it is important to emphasize that at lower temperatures the ground state of distorted octahedral Co 2+ is a Kramers doublet.…”

“…The Mo–O bond distances range from 1.729(4) to 1.815(4) Å with an average Mo–O bond distance of 1.761 Å which is consistent with the expected sum of the Shannon crystal radii, 1.79 Å, for a 4-coordinate high spin Mo 6+ and O 2− . 54…”

Nanocrystalline BaCo3(VO4)2(OH)2 with a kagome lattice of Co(ii) ions: synthesis, crystal structure and magnetic properties

“…23 The magnetization versus field variation is not saturated even at 2 K and 7 T. The maximum value of the magnetization at 2 K (40 emu g −1 ) corresponds to 1.4 μ B per Co-atom, which is lower than the saturation values observed in bulk oxides or orthovanadate compounds containing high-spin Co 2+ ions in octahedral environment. 8,9,21,22,24,25 The slope of the isothermal M ( H ) scan at high field ( H > 4 T) and low temperature ( T < 5 K) is at least four times higher than the Van Vleck paramagnetic susceptibility observed in high-spin Co 2+ compounds, 21,22 suggesting the presence of AF interactions and/or of magnetic anisotropy. Octahedral high-spin Co 2+ moments are often anisotropic due to spin–orbit coupling.…”

“…Published neutron diffraction results for high-spin Co 2+ oxide phases evidenced F interactions for Co–O–Co angles less than about 100°. 24,28 Recent theoretical studies for high-spin Co 2+ ion in 90° Co–O–Co bonding geometry with pseudo-spin J eff = 1/2 have suggested a more complex situation in which F anisotropic Kitaev interactions coexists with a Heisenberg coupling, that can be F or AF depending on the local electronic structure. 29,30 Further neighbours interactions could also play an important role, as suggested in BaCu 3 (VO 4 ) 2 (OH) 2 .…”

NaCo2(SeO3)2(OH): competing magnetic ground states of a new sawtooth structure with 3d7 Co2+ ions

“…38 We have successfully employed the hydrothermal method to synthesize numerous first-row transition metal [VO4] 3and [MoO4] 2-compounds which encouraged us to explore transition metal-based selenium(IV) oxyanions compounds and perform detailed physical property studies. [39][40][41][42][43][44][45][46][47][48][49][50][51] The realization of selenium(IV) oxyanions compounds targeting exotic magnetic properties has been very limited and only a handful of reports are available in the literature. Furthermore, selenium can adapt [SeO3] 2and [Se2O5]oxyanion configuration which can form a great number of different structural arrangements in extended solid structures providing a rich and diverse crystal chemistry.…”