Synthesis, structure, and magnetic properties of two quasi-low-dimensional antiferromagnets, NaMnAsO4 and β-NaCuPO4
作者:Mutlu Ulutagay-Kartin、Kristen M.S.G. Etheredge、George L. Schimek、Shiou-Jyh Hwu
DOI:10.1016/s0925-8388(02)00242-6
日期:2002.5
Crystals of NaMnAsO4 (1) and beta-NaCuPO4 (2) were grown by conventional high-temperature, solid-state methods in molten salt media. The compounds were characterized by single crystal X-ray diffraction and magnetic susceptibility measurements. Compound 1 crystallizes in an orthorhombic lattice with a=10.853(3) Angstrom, b=6.383(2) Angstrom, c=5.157(2) Angstrom, and V=357.2(2) Angstrom(3); Pnma (No. 62); Z=4, while 2 crystallizes in a monoclinic lattice with a=6.943(1) Angstrom, b=8.848(1) Angstrom, c=5.013(1) Angstrom. beta=97.25(1)degrees and V=305.53(9) Angstrom(3); P2(1)/n (No. 14); Z=4. The new sodium manganese(II) arsenate is isostructural with LiMnAsO4, which contains single layers of (100) perovskite sheet made of distorted MnO6 octahedra. Sodium copper(II) phosphate adopts a known beta-form that possesses linear chains of edge-shared CuO6 octahedra depicting a [4+2] Jahn-Teller distortion. These structurally isolated magnetic layers and chains are incorporated into a three-dimensional lattice via the linkage by closed-shell, non-magnetic oxy anions. Magnetic susceptibility measurements reveal that the title compounds are antiferromagnetic with the negative Weiss constants theta=-76.99 K (1) and -33.85 K (2). At low-temperatures, magnetic susceptibility data feature a field-induced antiferromagnetic-to-ferromagnetic transition. The field dependence studies further indicate that these phenomena could be attributed to metamagnetism and a spin-flop transition, respectively. The current work in the exploratory synthesis of quasi-low-dimensional TM-based oxy compounds gives a new perspective to the continued investigation of experimental and theoretical developments of magnetic models. (C) 2002 Elsevier Science B.V. All rights reserved.