Distinct effect of Kondo physics on crystal field splitting in electron and spin spectroscopies

TL;DR

This paper investigates how Kondo physics influences magnetic anisotropy in rare earth materials, revealing distinct effects on different spectroscopic measurements through numerical analysis of a minimal impurity model.

Contribution

It demonstrates the differential impact of Kondo physics on various experimental probes of magnetic anisotropy in a simplified impurity model.

Findings

Anisotropy suppresses Kondo screening.

Valence fluctuations enhance magnetic anisotropy.

Different spectroscopic methods show distinct renormalization effects.

Abstract

Magnetic anisotropy is a key feature of rare earth materials from permanent magnets to heavy fermions. We explore the complex interplay of Kondo physics and anisotropy, and their effect on different experimental probes of magnetic anisotropy in a minimal J = 3/2 Anderson impurity model using numerical renormalization group. While anisotropy suppresses Kondo screening, virtual valence fluctuations enhance the anisotropy. We find distinct renormalization of the magnetic anisotropy measured via dynamical spin response (inelastic neutron scattering) versus electronic excitations in the impurity spectral function (resonant inelastic x-rays and scanning tunneling spectroscopy). The two measurement types have different responses and dependences on the temperature and Kondo scales.