Thermodynamic and magnetic properties of intercalated layered compounds FexNbS2

Heat capacities and magnetic susceptibilities of single crystals of FexNbS2 (x=0.199 and 0.239) were measured at temperatures from 1.8 to 300 It and f rom 5 to 300 K, respectively. For Fe0.199NbS2, anomalies in the heat capaci ty and magnetic susceptibility were observed at 36 and 39 K, respectively. X noteworthy difference between held-cooled Xii (FC and zero field-cooled c hi (parallel to) (ZFC) below 60 K, supports the evidence of a spin-glass st ate for Fe0.199NbS2. An anomaly in the heat capacity was observed for Fe0.2 39NbS2 at 146.5 K, whereas the magnetic susceptibility displayed a maximum at 151 R, corresponding to an antiferro-paramagnetic phase transition. Heat capacity data of single crystal of Fe0.239NbS2 were in goad agreement with those of powdered sample at temperatures excluding an order-disorder phase transition. The experimental excess entropy of antiferro-paramagnetic phas e transition was calculated to be 8.4 J K-1 (mol Fe)(-1) for Fe0.239NbS2 an d compared with the theoretical value calculated on the basis of entropy an alysis. (C) 2001 Elsevier Science B.V. All rights reserved.