Field evolution of the spin-liquid candidate YbMgGaO$_4$

TL;DR

This study investigates the magnetic properties of YbMgGaO$_4$, a spin-liquid candidate, revealing nonmonotonic magnetization behavior and smeared plateaus due to disorder, using experimental measurements and Monte Carlo simulations.

Contribution

It provides the first detailed experimental and theoretical analysis of the field evolution in YbMgGaO$_4$, highlighting the effects of disorder on its magnetic plateaus.

Findings

Absence of the $rac13$ plateau phase.

Observation of plateau-like features at specific magnetic fields.

Disorder causes smearing of the $rac12$ plateau.

Abstract

We report magnetization, heat capacity, thermal expansion, and magnetostriction measurements down to millikelvin temperatures on the triangular antiferromagnet YbMgGaO$_4$. Our data exclude the formation of the distinct $\frac13$ plateau phase observed in other triangular antiferromagnets, but reveal plateaulike features in second derivatives of the free energy, magnetic susceptibility and specific heat, at $\mu_0H$ = 1.0 - 2.5 T for $H\parallel{}c$ and 2 - 5 T for $H\perp{}c$. Using Monte-Carlo simulations of a realistic spin Hamiltonian, we ascribe these features to nonmonotonic changes in the magnetization and the $\frac12$ plateau that is smeared out by the random distribution of exchange couplings in YbMgGaO$_4$.