Crystal structure and thermodynamic properties of NdCu4Au compound

We report the synthesis of the antiferromagnet cubic-type structure NdCu4Au derived by substituting Au for Cu in the parent binary NdCu5 compound. The room temperature X-ray diffraction analysis indicates a cubic MgCu4Sn-type structure with space group F 4 ¯ 3 m (No. 216) for the NdCu4Au compound. The thermodynamic properties of NdCu4Au have been probed by magnetic susceptibility, χ ( T ) , magnetization, M ( μ 0 H ) , and specific heat, Cp(T), measured down to 1.8 K. The low temperature χ ( T ) data shows probably an antiferromagnetic (AFM)-like anomaly associated with a Neel temperature TN=3.9 K. In the paramagnetic region, χ ( T ) data follows the modified Curie–Weiss law with an effective magnetic moment μ eff = 3.547 ( 5 ) μ B and Weiss temperature θ p = − 10.19 ( 8 ) K . The value for μeff is close to the value of 3.62 μB expected for the Nd3+-ion. No evidence of metamagnetic transition was observed from the isothermal M ( μ 0 H ) results. Cp(T) data confirm the AFM phase transition at TN=3.5 K close to the value of 3.9 K observed in χ ( T ) . The 4f-electron specific heat shows a Schottky-type anomaly around 20 K associated with crystalline-electric-field (CEF), with energy splitting Δ1=62(5) K and Δ2=109(9) K of the Nd3+ (J=9/2) multiplet, that are associated with the first and second excited state of Nd3+-ion. From the results of the 4f-electron magnetic entropy, it is speculated that the CEF ground state of Nd3+ (J=9/2) ions is the Γ6 doublet for NdCu4Au.