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Explorations of New Phases in the GaIII/InIII-CuII-SeIV-O System

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posted on 20.07.2009, 00:00 by Fang Kong, Qi-Pu Lin, Fei-Yan Yi, Jiang-Gao Mao
Four new gallium(III)/indium(III), copper(II), selenium(IV) oxides, namely, Ga2Cu(SeO3)4 (1), Ga2CuO(SeO3)3 (2), and M2Cu3(SeO3)6 (M = Ga 3, In 4), have been synthesized by hydrothermal or high-temperature solid-state reactions. The structure of Ga2Cu(SeO3)4 (1) features a 2D layer of corner-sharing GaO6 and CuO6 octahedra with the SeO3 groups hanging on both sides of the 2D layer. Ga2CuO(SeO3)3 (2) features a pillared layered structure in which the 1D Cu(SeO3)34− chains act as the pillars between 2D layers formed by corner- and edge-sharing GaOn (n = 4, 5) polyhedra. Although the chemical compositions of M2Cu3(SeO3)6 (M = Ga 3, In 4) are comparable, they belong to two different structural types. Ga2Cu3(SeO3)6 (3) exhibits a pillared layered structure built by [Ga2Cu3(SeO3)4]4+ thick layers with Se(3)O32− groups as pillars. The structure of In2Cu3(SeO3)6 (4) features a 3D network composed of [In2(SeO3)2]2+ layers and [Cu3(SeO3)4]2− layers interconnected through Se−O−Cu and In−O−Cu bridges, exhibiting 8-MR helical tunnels along the a-axis. Results of magnetic property measurements indicate that there are considerable antiferromagnetic interactions between copper(II) centers in Ga2CuO(SeO3)3 (2) and M2Cu3(SeO3)6 (M = Ga 3, In 4). Interestingly, Ga2Cu3(SeO3)6 (3) behaves as a weak ferromagnet below the critical temperature of Tc = 15 K. Further magnetic studies indicate that the compound is a canted antiferromagnet with a large canting angle of about 7.1°.