Electrical and Magnetic Properties of an Ising-type Ferromagnet NpSb₂

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We succeeded in growing a single crystal of NpSb₂ with the SmSb₂-type orthorhombic structure by the Sb-flux method and measured the electrical resistivity, specific heat, magnetic susceptibility and magnetization. NpSb₂ is found to be an Ising-type ferromagnet with the Curie temperature T_C=47 K, where the ordered moment of 1.6 μ_B/Np is oriented along the [001] direction. The electronic specific heat coefficient is estimated to be 22 mJ/(K²·mol). The electrical resistivity for the current J||[001] is by two orders of magnitude larger than that for J⊥[001], suggesting the quasi-two-dimensional electronic state.