Impurity-induced moment freezing in NaFe$_x$Ru$_{1-x}$O$_2$

TL;DR

This study investigates how magnetic impurity substitution in NaRuO$_2$ induces local spin freezing and alters magnetic behavior, revealing impurity-driven phenomena in a frustrated quantum magnetic system.

Contribution

It demonstrates impurity-induced spin freezing and Curie-Weiss behavior in NaRuO$_2$, providing new insights into impurity effects in quantum disordered magnets.

Findings

Local spin freezing observed with Fe substitution

Impurities induce Curie-Weiss magnetic behavior

Dynamic Ru moments are polarized around impurity sites

Abstract

We report the impact of magnetic impurity substitution on the quantum disordered magnetic ground state of NaRuO$_2$. Local $S=5/2$ moments are introduced into the frustrated triangular lattice of $J_{eff}=1/2$ Ru moments via Fe-substitution in NaFe$_x$Ru$_{1-x}$O$_2$, and the evolution of the magnetic ground state is reported. Local spin freezing associated with conventional spin glass behavior is observed upon Fe substitution, marking an impurity-induced freezing of the primarily dynamic magnetic ground state in NaRuO$_2$. Furthermore, local Fe moments induce a Curie-Weiss magnetic behavior in the uniform magnetic susceptibility, and the local moment magnitude is best described by dynamic Ru moments polarized about impurity sites. Our results establish an impurity-doping phenomenology consistent with inherently dynamic moments in NaRuO$_2$ that are pinned by local magnetic impurities, similar to ``swiss cheese" models of impurity-substituted copper oxides.