STRUCTURAL AND MAGNETIC-PROPERTIES OF THE TERNARY MANGANESE COMPOUND SEMICONDUCTORS MNAL2TE4, MNIN2TE4, AND MNIN2SE4

The tetragonal compounds MnAl2Te4 and MnIn2Te4 and the layered MnIn2Se4, with rhombohedral symmetry, are synthesized by melting a stoichiometric mixture of the elements or by chemical vapour transport technique. The temperature dependence of the lattice parameters shows a linear expansion with no structural transition. The magnetic susceptibility follows a Curie-Weiss behaviour but at low temperatures (< 70 K) deviations appear. The magnetic properties are discussed in terms of magnetic frustration in presence of chemical disorder of Mn and In or Al sites, preventing long-range order.