Structure and frustrated magnetism of the two-dimensional triangular lattice antiferromagnet Na2BaNi(PO4)2 * *Project supported by the National Natural Science Foundation of China (Grant No. 11804137) and the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2020YQ03 and ZR2018BA026).

Abstract

A new frustrated triangular lattice antiferromagnet Na2BaNi(PO4)2 was synthesized by high temperature flux method. The two-dimensional triangular lattice is formed by the Ni2+ ions with S = 1. Its magnetism is highly anisotropic with the Weiss constants θ CW = –6.615 K (H ⊥ c) and –43.979 K (H ∥ c). However, no magnetic ordering is present down to 0.3 K, reflecting strong geometric spin frustration. Our heat capacity measurements show substantial residual magnetic entropy existing below 0.3 K at zero field, implying the presence of low energy spin excitations. These results indicate that Na2BaNi(PO4)2 is a potential spin liquid candidate with spin-1.