Local spin polarization in underdoped cuprates with impurities

TL;DR

This paper develops a theoretical model explaining how magnetic and nonmagnetic impurities induce localized magnetic moments in underdoped cuprates, affecting their spin properties and NMR signals.

Contribution

It introduces a comprehensive theory of impurity-induced magnetism in underdoped cuprates, including the effects of AF correlations and Kondo screening.

Findings

Impurities induce magnetic moments on neighboring Cu sites.

Ni impurities partially screen the impurity spin, forming an effective S=1/2 moment.

The Kondo scale depends on the coupling constant via a power law.

Abstract

We present a theory of magnetic (Ni) and nonmagnetic (Zn) impurities substituted into planar Cu sites in the normal state of underdoped cuprates exhibiting a spin gap. Both types of impurities induce magnetic moments on neighboring Cu sites. In the case of Ni these moments partially screen the inherent impurity spin, resulting in an effective S=1/2 moment. The characteristic Kondo scale is found to have a power-law dependence on the coupling constant. We investigate the spatial shape of the impurity-induced spin density, taking into account the presence of short-ranged AF correlations, and calculate the ^{17}O NMR line broadening induced by impurity doping.