Field evolution of the spin-liquid candidate YbMgGa O4

Abstract

We report magnetization, heat capacity, thermal expansion, and magnetostriction measurements down to millikelvin temperatures on the triangular antiferromagnet YbMgGaO4. Our data exclude the formation of the distinct 13 plateau phase observed in other triangular antiferromagnets, but reveal plateaulike features in second derivatives of the free energy, magnetic susceptibility, and specific heat, at μ0H=1.0-2.5 T for H∥c and 2-5 T for H⊥c. Using Monte Carlo simulations of a realistic spin Hamiltonian, we ascribe these features to nonmonotonic changes in the magnetization and the 12 plateau that is smeared out by the random distribution of exchange couplings in YbMgGaO4. © 2020 American Physical Society.