Magnetic anomalies in the pseudoternary alloy series Ce₂Co_1−xAu_xSi₃

Abstract

We report the results of heat-capacity, magnetization, and electrical resistance measurements down to 2 K for a solid solution Ce₂Co_1−xAu_xSi₃, forming in a crystal structure derived from AlB₂-type hexagon. The results reveal that, at low temperatures, the magnetic ordering (setting in at a temperature below 8 K) dominates over the Kondo effect at the Au rich end, while the Kondo effect takes over for the Co rich end driving Ce₂CoSi₃ to nonmagnetism, with highest magnetic ordering temperature in this series for the composition range x=0.8-0.9. There appear to be dramatic changes in the magnetic structure with the variation of x, as well as with temperature (T) for some intermediate compositions in the magnetically ordered state, as inferred from the magnetization data. For those compositions (x=0.9 and 0.8) in which we observe double magnetic transitions as inferred from the heat-capacity data, field-cooled and zero-field-cooled magnetic susceptibilities deviate from each other for the lower-T (in the vicinity of 3-4 K) transition alone, as if the higher-T (around 7 K) transition is definitely not of a spin-glass type. These results, characterizing this solid solution as an interesting one, offer an opportunity to understand almost the entire range of Doniach's magnetic phase diagram in a single solid solution.