Evidence for competing magnetic instabilities in underdoped $\rm YBa_2Cu_3O_{6+x}$

TL;DR

This study uses polarized neutron scattering to investigate orbital-like magnetic order in underdoped YBa2Cu3O6+x, revealing a competition with electronic liquid crystal phases near a critical doping point, affecting magnetic properties.

Contribution

It provides new insights into how magnetic order in underdoped cuprates varies across the metal-insulator transition, highlighting the role of impurity substitution and phase competition.

Findings

Orbital-like magnetic order drops below the critical doping p_{MI}.

Impurity substitution affects the ordered magnetic moment but not the transition temperature.

Competition with electronic liquid crystal phases influences magnetic order near p_{MI}.

Abstract

We report a polarized neutron scattering study of the orbital-like magnetic order in strongly underdoped ${\rm YBa_2Cu_3O_{6.45}}$ and ${\rm YBa_2(Cu_{0.98}Zn_{0.02})_3O_{6.6}}$. Their hole doping levels are located on both sides of the critical doping $p_{MI}$ of a metal-insulator transition inferred from transport measurements. Our study reveals a drop down of the orbital-like order slightly below $p_{MI}$ with a steep decrease of both the ordering temperature $T_{mag}$ and the ordered moment. Above $p_{MI}$, substitution of quantum impurities does not change $T_{mag}$, whereas it lowers significantly the bulk ordered moment. The modifications of the orbital-like magnetic order are interpreted in terms of a competition with electronic liquid crystal phases around $p_{MI}$. This competition gives rise to a mixed magnetic state in ${\rm YBa_2Cu_3O_{6.45}}$ and a phase separation in ${\rm YBa_2(Cu_{0.98}Zn_{0.02})_3O_{6.6}}$.