Magnetic Phase Diagram of Triangular Lattice Eu-Based Compound EuAg\(_{4}\)Sb\(_{2}\)

We conducted a thorough study on the evolution of magnetic properties in the layered triangular lattice Eu-based antimonide EuAg \(_{4}\) $_4^{}$ Sb \(_{2}\) $_2^{}$ . The magnetic susceptibility measurements suggest that the title compound experiences two sequential antiferromagnetic transitions at approximately 10.8 K and 7.5 K, respectively, which is in contrast to the dominant ferromagnetic interactions indicated by a positive Curie-Weiss temperature in the paramagnetic region. This suggests the presence of a complex interaction between ferromagnetic and antiferromagnetic exchanges in EuAg \(_{4}\) $_4^{}$ Sb \(_{2}\) $_2^{}$ . The magnetic phase diagrams, constructed based on both magnetic susceptibility and isothermal magnetization measurements, provide unequivocal definitions for the various magnetic states observed in EuAg \(_{4}\) $_4^{}$ Sb \(_{2}\) $_2^{}$ . Remarkably, an intermediate transition state, accompanied by a 1/3 magnetization-plateau-like anomaly, emerges under in-plane magnetic fields, but missing under out-of-plane magnetic fields. Our result demonstrates that EuAg \(_{4}\) $_4^{}$ Sb \(_{2}\) $_2^{}$ hosts intriguing magnetic properties and could be a promising platform for exploring exotic magnetic properties of Eu \(^{2+}\) $_{}^{2+}$ triangular lattice compounds.