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 α-MnS, β-MnS and CuInS₂ in the range 0<x≤0.2 (≤0.6 for β-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, (2α-MnS)_x(CuInS₂)_1−x samples with 0.1<x≤0.2 and (2β-MnS)_x(CuInS₂)_1−x samples up to x=0.6 consist of two phases, occuring as tetragonal domains (x∼0.1 for X=S) within a cubic matrix with zinc-blende type structure (x∼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 (α-MnS with NaCl type structure, β-MnS with zinc-blende type structure) used during the synthesis. Additionally a CuMn_xIn_1−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 a long-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.