Investigation of the solid solution series 2(MnX)–CuInX 2 (X=S, Se)

Abstract

(2MnX) x (CuInX 2) 1− x with X=S and Se were prepared by solid state reaction from the end members α-MnS, β-MnS and CuInS 2 in the range 0< x≤0.2 (≤0.6 for β-MnS) as well as MnSe and CuInSe 2 in the range 0< x≤0.1. Mixed crystals with 0≤ x≤0.1 crystallize in the tetragonal chalcopyrite type structure, (2α-MnS) x (CuInS 2) 1− x samples with 0.1< x≤0.2 and (2β-MnS) x (CuInS 2) 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 x In 1− x S 2 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.