What Does The Korringa Ratio Measure?

TL;DR

This paper analyzes the Korringa ratio in disordered metals, showing how disorder and Stoner enhancement affect relaxation rates and the interpretation of experimental data, with applications to superconductors.

Contribution

It provides a detailed analysis of the Korringa ratio in dirty metals considering Stoner enhancement and disorder effects, offering insights into experimental interpretation.

Findings

Disorder significantly enhances relaxation rates.

Inverse problem solutions are constrained by disorder effects.

Preliminary applications to Rb$_{3-x}$K$_x$C$_{60}$ superconductors are discussed.

Abstract

We present an analysis of the Korringa ratio in a dirty metal, emphasizing the case where a Stoner enhancement of the uniform susceptibilty is present. We find that the relaxation rates are significantly enhanced by disorder, and that the inverse problem of determining the bare density of states from a study of the change of the Knight shift and relaxation rates with some parameter, such as pressure, has rather constrained solutions, with the disorder playing an important role. Some preliminary applications to the case of chemical substitution in the Rb$_{3-x}$K$_x $C$_{60}$ family of superconductors is presented and some other relevant systems are mentioned.