Magnetic and fermi surface properties in NpIn₃

We succeeded in growing a high-quality single crystal of NpIn₃ by the In-flux method, and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas-van Alphen (dHvA) effect. Ferromagnetic and antiferromagnetic orderings occur at T_C = 14K and T_N = 10 K, respectively, together with another transition at T* = 8 K. When the magnetic field is applied to the sample, the antiferromagnetic state is finally changed into a ferromagnetic state with two metamagnetic transitions. The antiferromagnetic ordering and two metamagnetic transitions are found to be of the first-order phase transition. In the dHvA experiments, we observed three dHvA branches with the cyclotron mass ranging from 3.4 to 14m₀. These dHvA branches are discussed from a viewpoint of the 5f-localized model based on the Fermi surface of LaIn₃.