Preparation and Characterization of a High-Entropy Magnet, (Mg, Mn, Co, Ni, Cu)3TeO6

We report on the synthesis of Mg_0.6Mn_0.7Co_0.7Ni_0.6Cu_0.4TeO₆, which is isostructural with multiferroic Mn₃TeO₆ (space group 𝑅3¯$R\overline{\mathrm{3}}$$R\overline{\mathrm{3}}$). Study of its magnetic properties indicates establishment of the long-range antiferromagnetic order at 16.3 K, slightly lower than that of pure Mn₃TeO₆. The tiny hysteresis of magnetization loop along with specific heat data implies the presence of ferromagnetic magnons at low temperatures. Dielectric measurements reveal sequence of well-defined steps in the real part of permittivity and peaks in the imaginary parts of permittivity at 30, 92, and 212 K attributable to the highly diffused structural changes, which are characteristic to relaxor ferroelectrics. It is shown that usual interpretation of this structure type as corundum-related is not accurate: the hexagonal oxygen packing is not close and is not double-layered. Therefore, Mn₃TeO₆ represents a very special structure type.