Low-temperature properties of Ga0.5Mo2S4

Specific heat measurements from 2 to 27 K and crystal structure and magnetic properties for 4.2–300 K are reported for the spinel Ga0.5Mo2S4. AtTp=42 K this ternary chalcogenide undergoes a phase transition. At liquid helium temperatures it has a rhombohedral crystal structure with lattice parametera=9.275 A and rhombohedral angle α=90.45°. It follows from the magnetization measurements that ferromagnetic ordering takes place at about 20 K, and close to the Curie point an anomaly in the temperature dependence ofCp has been found. The magnetic behavior of Ga0.5Mo2S4 at low temperatures can be explained by a small concentration of magnetic ions and far-distant-neighbor superexchange interactions partly weakened by vacancies located in 4(c) positions. Magnetocaloric measurements indicate the dominance of ferromagnetic interactions.