The First Vanadate–Carbonate, K₂Mn₃(VO₄)₂(CO₃): Crystal Structure and Physical Properties

Abstract

Mixed potassium-manganese vanadate-carbonate, K(2)Mn(3)(VO(4))(2)(CO(3)), represents a novel structure type; it has been synthesized hydrothermally from the system MnCl(2)-K(2)CO(3)-V(2)O(5)-H(2)O. Its hexagonal crystal structure was determined by single-crystal X-ray diffraction with a = 5.201(1) Å, c = 22.406(3) Å, space group P6(3)/m, Z = 2, ρ(c) = 3.371 g/cm(3), and R = 0.022. The layered structure of the compound can be described as a combination of honeycomb-type modules of [MnO(6)] octahedra and [VO(4)] tetrahedra, alternating in the [001] direction with layers of [MnCO(3)] built by [MnO(5)] trigonal bipyramids and [CO(3)] planar triangles, sharing oxygen vertices. The K(+) ions are placed along channels of the framework, elongated in the [100], [010], and [110] directions. The title compound exhibits rich physical properties reflected in a phase transition of presumably Jahn-Teller origin at T(3) = 80-100 K as well as two successive magnetic phase transitions at T(2) = 3 K and T(1) = 2 K into a weakly ferromagnetic ground state, as evidenced in magnetization, specific heat, and X-band electron spin resonance measurements. A negative Weiss temperature Θ = -114 K and strongly reduced effective magnetic moment μ(eff)(2) ~ 70 μ(B)(2) per formula unit suggest that antiferromagnetic exchange interactions dominate in the system. Divalent manganese is present in a high-spin state, S = 5/2, in the octahedral environment and a low-spin state, S = ½, in the trigonal-bipyramidal coordination.

Sodium Transition Metal Vanadates from Hydrothermal Brines: Synthesis and Characterization of NaMn4(VO4)3, Na2Mn3(VO4)3, and Na2Co3(VO4)2(OH)2

“…Such edge shared 2‐D planar systems are of interest because they often display interesting magnetic properties and thus merit a more detailed examination , . We recently observed a topologically similar structure in the alkali transition metal molybdate systems, where KMn 3 (MoO 4 ) 2 O(OH) was found to have an ideal Kagome layer in space group R 3 m .…”

Joint crystallization of KCuAl[PO4]2 and K(Al,Zn)2[(P,Si)O4]2: crystal chemistry and mechanism of formation of phosphate-silicate epitaxial heterostructure

“…The promise of fluoro-phosphates and vanadates as magnetically and electrochemically active materials has been shown in recent research [see, for example, Keates et al (2013)]. Novel materials based on phosphates with 2D and 1D subsystems of the magnetic structure, formed by first-row transition metals, show highly functional characteristics, inherent to frustration of the exchange interaction of magnetically active ions (Shvanskaya et al, 2015;Yakubovich, Kiriukhina et al, 2013;Yakubovich, Yakovleva et al, 2013). Research into the physical properties of such objects lies in the field of quantum cooperative phenomena and contributes to the development of theoretical ideas about the structure of matter (Lin & Ding, 2013).…”

Exotic Magnetic Field-Induced Spin-Superstructures in a Mixed Honeycomb-Triangular Lattice System

“…The vanadate -carbonate system K 2 Mn 3 (VO 4 ) 2 CO 3 has been recently identified as a very promising prototype for studying magnetic frustration. [33,34] Its structure, shown in Fig. 2, consists of alternately stacked triangular and honeycomb magnetic layers.…”

“…It was inferred that divalent Mn is present in a high-spin state (S = 5/2) in the octahedral environment of the honeycomb layer and a low-spin state (S = 1/2) in the trigonal bipyramidal coordination of the Mn 2+ ions occupying the triangular layer. [33] The low-temperature magnetic transitions were attributed to the ordering of the S = 5/2 ions of the honeycomb lattice , while the S = 1/2 triangular layers were thought to remain paramagnetic. Subsequent first-principles density functional theory-based analysis showed that, contrary to the previous suggestion, both inequivalent Mn ions occupying the two layers are in high-spin S = 5/2 state.…”