Kondo and magnetic ordering anomalies in Ce_2-xPtSi₃ (R=La, Y)

Abstract

The compound Ce₂PtSi₃ crystallizing in the AlB₂-derived hexagonal structure has been known to undergo magnetic ordering around (T₀=) 5.5 K. We have investigated the influence of positive and negative chemical pressure on the Kondo effect and T₀ by studying Y and La substituted pseudo-ternary solid solutions Ce_2-xR_xPtSi₃ (R= La, Y) by AC and DC magnetic susceptibility, and heat capacity measurements. We find that the dilution of Ce sub-lattice by Y substitution is less effective in reducing T₀ when compared with La substituted series. The Kondo temperature as inferred from paramagnetic Curie temperature undergoes an increase with increasing La content, rather than a decrease usually expected for weakening Kondo effect following lattice expansion. This unusual Kondo and magnetic ordering behavior of this solid solution possibly arises from disorder and/or structural features.