PHASE-TRANSITIONS AT HIGH-TEMPERATURE IN INTERCALATION COMPOUNDS MN1 4NBS2 AND MN1/4TAS2/

Phase transitions in intercalation compounds MnxNbS2 and MnxTaS2 (x=1/ 4 and 1/3) have been investigated at high-temperature region using a m agnetic balance and an X-ray diffractometer. In Mn1/4NbS2, the discont inuous changes of the magnetic susceptibility and the lattice paramete r c are observed at 640 K. In Mn1/4TaS2, similar discontinuities are. observed at 670 K. From the temperature dependence of the superlattice reflections, it has been found that these discontinuities are manifes tation of the structural phase transition associated with the order-di sorder of the intercalated Mn atoms and the displacement of the Nb, Ta and S atoms.