Normal State Magnetic Properties of Ni and Zn Substituted in YBa_{2}Cu_{3} O_{6+x}: Hole-Doping Dependence

TL;DR

This study uses SQUID and NMR techniques to accurately measure magnetic susceptibilities in Zn and Ni substituted YBa2Cu3O6+x across various doping levels, revealing minimal Weiss temperatures and doping-dependent magnetic moments.

Contribution

It provides precise susceptibility measurements and insights into magnetic screening effects and impurity-induced moments in hole-doped cuprates, a novel combination of techniques and doping range.

Findings

Weiss temperature is very small across all doping levels.

Zn induces a small magnetic moment that decreases with doping.

Ni maintains a nearly constant spin-1/2 magnetic moment regardless of doping.

Abstract

We present SQUID susceptibility data on Zn and Ni substituted YBa_{2}Cu_{3}O_{6+x}. Cross-checks with NMR yield an unprecedented accuracy in the estimate of the magnetic susceptibility associated with the substituants, from the underdoped to the lightly overdoped case. This allows us to determine the Weiss temperature \theta for YBCO: its value is very small for all hole dopings n_h. Since in conventional metals, the Kondo temperature, $T_{K}<\theta$, magnetic screening effects would not be expected for $T\gg \theta$; in contrast, increasing n_h produces a reduction of the small moment induced by Zn^{2+} and a nearly constant effective moment for Ni^{2+} corresponding to a spin 1/2 rather than to a spin 1.