Field evolution of the spin-liquid candidate YbMgGaO4

We report magnetization, heat capacity, thermal expansion, and magnetostriction measurements down to millikelvin temperatures on the triangular antiferromagnet $\mathrm{Yb}\mathrm{Mg}\mathrm{Ga}{\mathrm{O}}₄$. Our data exclude the formation of the distinct $\frac{1}{3}$ plateau phase observed in other triangular antiferromagnets, but reveal plateaulike features in second derivatives of the free energy, magnetic susceptibility, and specific heat, at ${\ensuremath{\mu}}₀H=1.0--2.5$ T for $H\phantom{\rule{0.16em}{0ex}}\ensuremath{\parallel}\phantom{\rule{0.16em}{0ex}}c$ and $2--5$ T for $H\ensuremath{\perp}c$. Using Monte Carlo simulations of a realistic spin Hamiltonian, we ascribe these features to nonmonotonic changes in the magnetization and the $\frac{1}{2}$ plateau that is smeared out by the random distribution of exchange couplings in $\mathrm{Yb}\mathrm{Mg}\mathrm{Ga}{\mathrm{O}}₄$.