Magnetic ordering of the Mn sublattice: Dense Kondo-lattice behavior of Ce in (RPd3)8Mn (R=La, Ce)

We have synthesized interstitial compounds (RPd 3 ) 8 Mn (R=La and Ce). The Mn ions in these compounds, present in "dilute" concentrations of just 3 molar percent, form a regular sublattice with an unusually large Mn-Mn near-neighbor distance of ∼8.5 A. While the existence of (RPd 3 ) 8 M (M: p-block element) is already documented in the literature, the present work reports on the formation of this phase with M being a 3d element. In (LaPd 3 ) 8 Mn, the Mn sublattice orders antiferromagnetically, as inferred from the peaks in low-field magnetization at 48 and 23 K. The latter peak progressively shifts towards lower temperatures in increasing magnetic field and disappears below 1.8 K in a field of ∼8 kOe. On the other hand, in (CePd 3 ) 8 Mn the Mn sublattice undergoes a ferromagnetic transition around 35 K. The Ce ions form a dense Kondo lattice and are in a paramagnetic state at least down to 1.5 K. A strongly correlated electronic ground state, arising from the Kondo effect, is inferred from the large extrapolated value of C/T=275 mJ/mol Ce K 2 at T=0 K.