Synthesis, crystal structure, and magnetic properties of the oxometallates KBaMnO4 and KBaAsO4

Abstract

Single crystals of KBaMnO 4 and KBaAsO 4 were grown using the hydroflux method and characterized by single crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Pnma with a = 7.7795(4) Å, b = 5.8263(3) Å, and c = 10.2851(5) Å for the manganate and a = 7.7773(10) Å, b = 5.8891(8) Å, and c = 10.3104(13) Å for the arsenate. The materials exhibit a threedimensional crystal structure consisting of isolated MnO 4 3or AsO 4 3tetrahedra, with the charge balance maintained by K + and Ba 2+. Each tetrahedron is surrounded by six K + and five Ba 2+ , and shares its corner/edge with KO 10 polyhedra and corner/edge/face with BaO 9 polyhedra, respectively. The crystal growth, crystal structure and magnetic properties are discussed.

Hydroflux Synthesis and Characterization of the Non‐Centrosymmetric Oxomanganate(V) KSrMnO4

“…Similar observations were reported for the synthesis of KBaMnO 4 . [17] The product obtained after washing was phase-pure according to visual inspection and powder X-ray diffraction (PXRD; Figure S2, Supporting Information). Oxomanganate(V) is known to disproportionate in alkaline solution at room temperature to oxomanganate (VI) and MnO 2 , whereby lower temperature and higher base concentration decelerate this reaction.…”

“…These bond lengths do not differ by more than 1 % to Mn-O distances of other oxomanganates(V) with alkali and/ or alkaline-earth elements. [12][13][14][15][16][17] The [MnO 4 ] 3tetrahedron is slightly distorted with O-Mn-O angles between 105.1(1)°and ARTICLE 113.0(1)°. The two smallest angles, 105.1(1)°and 107.5(1)°, are located at edges, where a strontium-centerd polyhedron is attached.…”

“…KBaMnO 4 crystallizes in Pnma (Figure 3), [17] which is reached by removing the centering of Cmcm. In this k2 transition (klassengleich of index 2), the dimensions of the unit cell remain basically the same, but axes and origin have to be changed to comply with the standard setting.…”

“…KSrMnO 4 is paramagnetic at room temperature and orders antiferromagnetically below T N = 4.6(1) K. The low Néel temperature can be rationalized by the isolated [ In KBaMnO 4 , the Mn-Mn distances are more than 25 pm longer and, correspondingly, the Néel temperature is about 1 K lower than in the strontium compound. [17] The inverse susceptibility vs. T data was fitted in the paramagnetic regime with a ARTICLE Figure 6. Magnetic susceptibility of KSrMnO 4 in an external field of 10 mT, and linear fit of the inverse magnetic susceptibility according to a Curie-Weiss law.…”

“…[6] The known oxidic manganese(V) compounds primarily comprise perovskites, [2,7] apatites, [8][9][10] some doped oxides, [1,11] and several oxomanganates(V) with elements of the first two groups of the periodic Table. [12][13][14][15][16][17] Most of the reported manganese(V) oxides were synthesized by solid-state reaction. [1][2][3][4][7][8][9][12][13][14][15][16] Recently, zur Loye et al presented the oxomanganates(V) compounds A 5 [MnO 4 ] 3 OH (A = Sr, Ba) [10] and KBaMnO 4 , [17] which they obtained via the hydroflux method.…”