Investigation of the solid solution series 2(MnX)-CuInX2 (X = S, Se)

(2MnX)(x)(CuInX2)(1-x) with X = S and Se were prepared by solid state reaction from the end members alpha-MnS, beta-MnS and CuInS2 in the range 0 < x <= 0.2 (<= 0.6 for beta-MnS) as well as MnSe and CuInSe2 in the range 0 < x < 0.1. Mixed crystals with 0 < x < 0.1 crystallize in the tetragonal chalcopyrite type structure, (2 alpha-MnS)(x)(CuInS2)(1-x) samples with 0.1 < x <= 0.2 and (2 beta-MnS)(x)(CuInS2)(1-x) samples up to x = 0.6 consist of two phases, occuring as tetragonal domains (x similar to 0.1 for X = S) within a cubic matrix with zinc-blende type structure (x similar to 0.4 for X = S), indicating a miscibility gap. For tetragonal single phase samples the band gap energy, the lattice constants and the anion parameter have been determined. The first and the latter ones show a different composition dependent behaviour caused by the modification of the MnS (alpha-MnS with NaCl type structure, beta-MnS with zinc-blende type structure) used during the synthesis. Additionally a CuMnxIn1-xS2 powder sample, in which Mn substitutes the M-III site, was investigated. The SQUID measurements revealed a well-distinct magnetic transition between 15 and 16 K as well as ferromagnetic-like hysteresis loops pronounced for temperatures below the transition temperature. Below this temperature a clear splitting between the zero field cooling (ZFC) and the field cooling (FC) curves indicate to the existence of along-range magnetic ordering phenomenon. This behaviour was not found in the other samples were Mn substitutes both sites M-I as well as M-III. (c) 2005 Elsevier Ltd. All rights reserved.