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

Abstract

We have synthesized two new interstitial compounds (RPd 3 ) 8 Mn (R = La and Ce). The Mn ions present in 'dilute' concentration of just 3 molar percent form a sublattice with an unusually large Mn-Mn near neighbor distance of ∼8.5Å. While the existence of (RPd 3 ) 8 M (where M is a p-block element) is already documented in the literature, the present work reports for the first time the formation of this phase with M being a 3d element. In (LaPd 3 ) 8 Mn, the Mn sub-lattice orders antiferromagnetically as inferred from the peaks in low-field magnetization at 48 K 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 Kondo effect is inferred from the large extrapolated value of C/T = 275 mJ/Ce-mol K 2 at T = 0 K. In contrast, the interstitial alloys RPd 3 Mn x (x = 0.03 and 0.06), also synthesized for the first time, have a spin glass ground state due to the random distribution of the Mn ions over the available 1b sites in the parent RPd 3 crystal lattice.