# Spin-glass state and reversed magnetic anisotropy induced by Cr doping in the Kitaev magnet $\alpha$-RuCl$_3$

## TL;DR

This study explores how Cr doping in $ ext{RuCl}_3$ alters its magnetic properties, inducing a spin-glass state and reversing magnetic anisotropy due to competing interactions between Ru and Cr ions.

## Contribution

It demonstrates the emergence of a spin-glass state and reversed magnetic anisotropy in Cr-doped $ ext{RuCl}_3$, revealing the interplay of anisotropic and isotropic magnetic interactions.

## Key findings

- Reversal of magnetic anisotropy with Cr doping.
- Destabilization of long-range order leading to spin-glass state.
- Maximum freezing temperature at intermediate Cr content.

## Abstract

Magnetic properties of the substitution series Ru$_{1-x}$Cr$_x$Cl$_3$ were investigated to determine the evolution from the anisotropic Kitaev magnet $\alpha$-RuCl$_3$ with $J_{\rm eff} = 1/2$ magnetic Ru$^{3+}$ ions to the isotropic Heisenberg magnet CrCl$_3$ with $S = 3/2$ magnetic Cr$^{3+}$ ions. Magnetization measurements on single crystals revealed a reversal of the magnetic anisotropy under doping, which we argue to arise from the competition between anisotropic Kitaev and off-diagonal interactions on the Ru-Ru links and approximately isotropic Cr-Ru and isotropic Cr-Cr interactions. In addition, combined magnetization, ac susceptibility and specific-heat measurements clearly show the destabilization of the long-range magnetic order of $\alpha$-RuCl$_3$ in favor of a spin-glass state of Ru$_{1-x}$Cr$_x$Cl$_3$ for a low doping of $x\backsimeq0.1$. The corresponding freezing temperature as a function of Cr content shows a broad maximum around $x\backsimeq0.45$.