Single crystals of the shandite-type half metallic ferromagnet Co3Sn2S2, and its In-substituted compounds, Co3Sn2−xInxS2 (0<x≤2) were grown by a flux method. We report optimum conditions to synthesize large crystals. Single crystals of the two end members, Co3Sn2S2 and Co3In2S2, and solid solutions with low In concentrations (x≤0.35) were grown out of Sn and In self flux. Solid solution single crystals with higher In concentrations were grown out of Sn, In and Pb mixture flux. Grown crystals were characterized using the powder x-ray diffraction, wavelength-dispersive x-ray spectroscopy and magnetization measurements. The shandite structure with R3̄m symmetry was confirmed and crystal structure parameters of the obtained plate-shaped hexagonal crystals were refined using the Rietveld analysis. Magnetization measurements show suppression of the ferromagnetic ordering, observed in Co3Sn2S2, by In-substitution as reported for polycrystalline samples. The obtained crystals are useful to study anisotropy in magnetic and transport properties and further interesting magnetotransport properties of the layered compounds.
Keywords
A1. Low dimensional structuresA1. X-ray diffractionA1. Single crystal growthB1. SulfidesB2. Magnetic materials.
1. Introduction
Shandite compounds with the general formula T3M2X2 crystallize isostructuraly to the mineral shandite Ni3Pb2S2[1]. Here T is Ni or Co; M is In, Sn, Pb or Tl; and X is a chalcogen element, S or Se. The shandites show a low dimensional crystal structure and fascinating electronic properties that have been studied extensively in recent decades [2–5]. The crystallographic and electronic structures of monoclinic parkerite (BiNi3/2S) and several shandites (MT3/2X), which are classified as ordered half antiperovskites, have been investigated by x-ray diffraction (XRD) and band structure calculations [6–10]. Fig. 1 shows the shandite type crystal structure of T3M2X2 which belongs to the trigonal space group R3̄m. The T and X atoms occupy the Wyckoff positions 9e (1/2,0,0) and 6c (0,0,z), respectively, and the M atoms occupy two positions, 3b (0,0,1/2) and 3a (0,0,0). The shandite-type crystal can be considered to consist of metallic layers stacked in ABC fashion along c-direction in a hexagonal notation. The layers are arranged in the kagomé network of the T atoms and triangular one of the intra-layer M atoms on 3a-site (M2). X and M atoms on 3b (M1) locate at interlayer positions. Each T atom is octahedrally surrounded by two M1, two M2 and two X atoms.