PREPARATION AND MAGNETIC-PROPERTIES OF RARE-EARTH PENTAMOLYBDENUM OCTAOXIDES [REMO(5)O(8)(RE=LA, CE, PR, ND AND SM)]

We present the synthesis of the REMo(5)O(8) compounds with RE = La, Ce, Pr, Nd and Sm. These compounds which crystallize in the space group P2(1)/c are characterized by infinite chains of bioctahedral Mo10O18 cluster units. First magnetic de measurements performed on these compounds are also reported. The La compound shows a temperature independent susceptibility with an anomaly at 13 K which could be associated to a phase transition. The Ce, Pr and Nd members have a nearly RE(3+) free ion behaviour at high temperature. Finally, the temperature dependence of the magnetic susceptibility of SmMo5O8 depends on the cooling mode (zero-field cooled or field cooled). This behaviour seems to be due a spin glass transition.