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, CeAu 2 Si 2 , CePd 2 Si 2 and CeAl 2 , 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 CeAl 2 , 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 there is relatively more 4f-localization as the particle size is reduced, resulting in weakening of exchange interaction strength.