Contrasting magnetic behavior of fine particles of some Kondo lattices

Abstract

We have investigated the magnetic behavior of ball-milled fine particles of well-known Kondo lattices, CeAu₂Si₂, CePd₂Si₂ and CeAl₂, by magnetization and heat-capacity studies in order to understand the magnetic behavior when the particle size is reduced. These compounds have been known to order antiferromagnetically in the bulk form near (T_N=) 10, 10 and 3.8 K respectively. We find that the features due to magnetic ordering get suppressed to temperatures below 1.8 K in the case of fine particles of ternary alloys, though trivalence of Ce as inferred from the effective moment remains unchanged. In contrast to this, in CeAl₂, there appears to be a marginal enhancement of T_N, when the particle size is reduced to less than a micron. These results can be consistently understood by proposing that these compounds move toward left in the Doniach magnetic phase-diagram, for instance, due to relatively more 4f-localization, as the particle size is reduced.