$\hat{I}¼$SR study of triangular Ising antiferromagnet ErMgGaO${}_4$

Abstract

We present a detailed magnetic study of the triangular antiferromagnet ErMgGaO${}_4$. A point charge calculation under the single ion approximation reveals a crystal field ground state doublet with a strong Ising-like behavior of the Er${}^{3+}$ moment along the c axis. Magnetic susceptibility and specific heat measurements indicate no presence of magnetic transitions above 0.5~K and no evidence of residual entropy as temperature approaching zero. Zero field (ZF) $\hat{I}¼$SR measurements shows no sign of static uniform or random field and longitudinal field (LF) $\hat{I}¼$SR measurements exhibit persistent spin fluctuations down to our lowest temperature of 25~mK. Our results provide evidence of a quantum spin liquid state in the triangular antiferromagnet ErMgGaO${}_4$.