Magnetic phase diagram and multiple field-induced states in the intermetallic triangular-lattice antiferromagnet NdAuAl4Ge2 with Ising-like spins

Geometrical frustration and the enhancement of strong quantum fluctuations in two-dimensional triangular antiferromagnets can lead to various intriguing phenomena. Here, we studied the spin-1/2 triangular lattice antiferromagnet NdAuAl4Ge2. Thermodynamic and transport properties, such as magnetization and specific heat together with the resistivity measurements were performed. In zero field, two successive phase transitions were observed at T-N1 = 1.75 +/- 0.02 and T-N2 = 0.49 +/- 0.02 K, respectively. Under magnetic field, XXZ-type anisotropy was revealed with the moments pointing along the easy c axis. For B parallel to c, multiple field-induced states were observed, and the magnetic phase diagram was established based on the specific-heat and magnetization data. The temperature-dependent resistivity measurements indicate that NdAuAl4Ge2 is a good metal. It is very likely that both the long-range Ruderman-Kittel-Kasuya-Yosida interactions and the geometrical frustration play important roles in this case.