Heat capacity and phase transition of Fe NbS2 at low temperature

Heat capacities of single crystals of Fe x NbS 2 ( x =0.159, 0.281, 0.309 and 0.325) were measured at temperatures from 1.8 to 100 K. Heat capacity anomalies were observed in all of the single crystals. Both Fe 0.325 NbS 2 and Fe 0.309 NbS 2 underwent the successive three magnetic phase transitions around 40 K. The successive phase transitions originate in the √3 a ×√3 a superstructure in-plane of Fe 1/3 NbS 2 . A phase diagram of Fe x NbS 2 system was established from the obtained temperatures of magnetic phase transition and spin-glass like transition.