MULTIPLE PHASE-TRANSITIONS IN CERU2(SI1-XGEX)(2)

The magnetic-phase diagram of the system CeRu2(Si1-xGex)(2) is studied by specific-heat, magnetic-susceptibility and electrical resistance m easurements (x = 0.1, 0.2, 0.3, 0.6, 0.8, 0.9, 1.0). The susceptibilit y chi was measured by zero-field-cooling (ZFC) and field-cooling (FC) methods. If x < 0.1, there is no clear long-range magnetic order. When x > 0.1, chi(FC)(T) starts to deviate from chi(ZFC)(T) at T-sf. This suggests a spin-glass state below T-sf. In the range 0.9 greater than or equal to x greater than or equal to 0.2, the specific-heat measurem ents of CeRu2(Si1-xGex)(2) show multiple magnetic phase transitions. T here are three phase transitions in CeRu2Si0.4Ge1.6 and CeRu2Si0.2Ge1. 8. Except for x = 0, below 30 K, electrical resistivity rho(T) increas es continuously up to a temperature of 10 K. The drastic drop of p(T) below 10 K is due to magnetic ordering. The multiple phase transitions of CeRu2 (Si1-xGex)(2) are not observed in the resistance measurement s. However, the slope of rho(T)/rho(285 K) of CeRu2Si0.4Ge1.6 changes at similar to 7 K, which further supports multiple phase transitions i n CeRu2(Si1-xGex)(2).