Calculations of the Knight Shift Anomalies in Heavy Electron Materials

TL;DR

This paper investigates the Knight shift anomalies in heavy electron materials using the infinite U Anderson model and NCA, comparing theoretical calculations with experimental data across various compounds.

Contribution

It provides a systematic analysis of Knight shift and susceptibility in heavy electron systems, incorporating lattice coherence and multiple rare earth shells, with comparisons to experimental results.

Findings

Low temperature Knight shift anomalies increase with Kondo temperature and distance.

Theoretical results match experimental data for CeSn_3, YbCuAl, and Y_{0.8}U_{0.2}Pd_{3}.

Lattice coherence effects significantly influence Knight shift behavior.

Abstract

We have studied the Knight shift $K(\vec r, T)$ and magnetic susceptibility $\chi(T)$ of heavy electron materials, modeled by the infinite U Anderson model with the NCA method. A systematic study of $K(\vec r, T)$ and $\chi(T)$ for different Kondo temperatures $T_0$ (which depends on the hybridization width $\Gamma$) shows a low temperature anomaly (nonlinear relation between $K$ and $\chi$) which increases as the Kondo temperature $T_0$ and distance $r$ increase. We carried out an incoherent lattice sum by adding the $K(\vec r)$ of a few hundred shells of rare earth atoms around a nucleus and compare the numerically calculated results with the experimental results. For CeSn_3, which is a concentrated heavy electron material, both the ^{119}Sn NMR Knight shift and positive muon Knight shift are studied. Also, lattice coherence effects by conduction electron scattering at every rare earth site are included using the average-T matrix approximation. Also NMR Knight shifts for YbCuAl and the proposed quadrupolar Kondo alloy Y_{0.8}U_{0.2}Pd_{3} are studied.