Advanced Physical Research

The rich surface-state physics of topological insulators underscores the importance of tuning their properties and developing efficient compounds. Motivated by the pressure-dependent superconductivity of GeSb₄Te₇ and MnSb₄Te₇, and the antiferromagnetism of the latter, we report the synthesis of GeSb₄Te₇–MnSb₄Te₇ solid solutions, enabled by their structural similarity and the comparable ionic radii of Mn²⁺ and Ge²⁺. As it was shown by PXRD analyses that around ~50 % solubility of Mn at Ge sites in GeSb₄Te₇ was successfully achieved, while compositions with higher Mn substitutions (70% and 90%) and pristine MnSb₄Te₇ formed multiphasic mixtures consisting of phases based on GeSb₄Te₇, MnSb₂Te₄, and Sb₂Te₃. Le Bail analysis revealed that lattice parameter a increases almost linearly with increasing Mn content, while lattice parameter c decreases almost linearly – a trend that is unexpected, but consistent with observations in the Bi-based sister system. The middle range 50 % Mn substitution compound was selected for SQUID magnetometry, revealing two magnetic transitions at 14.4 K and 3.6 K, which correspond to paramagnetic-to-ferrimagnetic and ferrimagnetic-to-ferromagnetic transitions, respectively. Both effective and saturation magnetic moments decreased significantly compared to pristine MnSb₄Te₇, due to magnetic dilution from Ge ions and Mn ions present at Sb sites, both of which induce intralayer antiferromagnetic coupling. These findings facilitate the selection of compositions for single-crystal growth and subsequent investigations of magneto-transport properties and topological surface states.