Synthesis, magnetization, and heat capacity of triangular lattice materials NaErSe2 and KErSe2

In this paper we report the synthesis, magnetization, and heat capacity of the frustrated magnets AErSe2(A=Na,K) which contain perfect triangular lattices of Er3+. The magnetization data suggests no long-range magnetic order exists in AErSe2(A=Na,K), which is consistent with the heat capacity measurements. Large anisotropy is observed between the magnetization within the ab plane and along the c axis of both compounds. When the magnetic field is applied along the ab plane, anomalies are observed at 1.8 μB in NaErSe2 at 0.2 T and 2.1 μB in KErSe2 at 0.18 T. Unlike NaErSe2, a plateaulike field-induced metamagnetic transition is observed for Hc below 1 K in KErSe2. Two broad peaks are observed in the heat capacity below 10 K indicating possible crystal electric field (CEF) effects and magnetic entropy released under different magnetic fields. All results indicate that AErSe2 are strongly anisotropic, frustrated magnets with field-induced transition at low temperature. The lack of signatures for long-range magnetic order implies that these materials are candidates for hosting a quantum spin liquid ground state.