Magnetic ordering and the Kondo effect in the alloys, Ce2Co1-xPdxSi3

The compound Ce-2 CoSi3, crystallizing in a AlB2-derived hexagonal structur e, has been recently identified as a Kondo lattice with a non-magnetic grou nd state. Here, we report the influence of gradual replacement of Co by Pd on the magnetic behaviour in the pseudo-ternary solid solution, Ce2Co1-xPdx Si3, by magnetization (2-300 K), electrical resistivity (2-300 K) and heat- capacity (0.7-30 K) measurements to bring out a transformation from non-mag netic to magnetic ordering. Distinct features attributable to the existence of a competition between the Kondo effect and magnetic ordering with varyi ng x and temperature are observed in the electrical resistivity data. The r esults reveal that small substitutions of Pd (x = 0.2-0.3) are sufficient t o induce magnetic ordering of the Ce ions at low temperatures. The strength of the Kondo interaction as indicated by the paramagnetic Curie temperatur e decreases monotonically with increasing Pd content. A notable finding is that there are qualitative changes in the isothermal magnetization data in the magnetically ordered state, as if there are modifications in the magnet ic structure with changes in the Co/Pd composition. The importance of elect ronic structure relative to unit-cell volume in deciding magnetic character istics of this class of compounds is brought out taking into account the tr ends in the magnetic behaviour of isostructural Ce compounds. (C) 2001 Else vier Science B.V. All rights reserved.