Multiple phase transitions in

Abstract

The magnetic-phase diagram of the system is studied by specific-heat, magnetic-susceptibility and electrical resistance measurements (x = 0.1, 0.2, 0.3, 0.6, 0.8, 0.9, 1.0). The susceptibility 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, starts to deviate from at . This suggests a spin-glass state below . In the range , the specific-heat measurements of show multiple magnetic phase transitions. There are three phase transitions in and . Except for x = 0, below 30 K, electrical resistivity increases continuously up to a temperature of 10 K. The drastic drop of below 10 K is due to magnetic ordering. The multiple phase transitions of are not observed in the resistance measurements. However, the slope of of changes at , which further supports multiple phase transitions in .