Experimental study of the competition between Kondo and RKKY interactions for Mn spins in a model alloy system

TL;DR

This study investigates the interplay of Kondo and RKKY interactions in Mn spins within a quasicrystal alloy, revealing that magnetization can be decomposed into independent Kondo and RKKY contributions across various concentrations and conditions.

Contribution

It demonstrates that magnetization in Mn-doped quasicrystals can be described as a sum of independent Kondo and RKKY effects without assuming a specific model, even at high RKKY dominance.

Findings

Magnetization decomposes into separate Kondo and RKKY contributions.

Kondo temperature found to be 3.35K across samples.

Independence of Kondo and RKKY effects persists up to high RKKY dominance.

Abstract

The quasicrystal Al-Pd-Mn is a model system for an experimental study of the competition between Ruderman-Kittel-Kasuya-Yoshida (RKKY) and Kondo interactions. First, specific of such alloys, only a few Mn atoms carry an effective spin and their concentration x is tunable over several orders of magnitude, even though the Mn amount is almost constant. Second, the characteristic energy scales for the interactions lie in the Kelvin range. Hence we could study the magnetization on both side of these energy scales, covering a range of temperatures [0.1-100 K] and magnetic fields (mu_B H/k_B= 0 to 5 K) for 22 samples and x varying over 2 decades. Using very general Kondo physics arguments, and thus carrying out the data analysis with no preconceived model, we found a very robust and simple result: The magnetization is a sum of a pure Kondo (T_K=3.35K) and a pure RKKY contributions, whatever the moment concentration is and this surprisingly up to the concentration where the RKKY couplings dominate fully and thus cannot be considered as a perturbation.