Crystal structure and thermodynamic properties of NdCu4Au compound

• We synthesized and characterized a new material.
• We investigated the ground state properties of this material from magnetic susceptibility, magnetization and heat capacity measurements.
• Antiferromagnetic ordering at low temperatures was observed.
• A Schottky-type anomaly associated with crystal electric-field effect was observed.

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 F4¯3m (No. 216) for the NdCu4Au compound. The thermodynamic properties of NdCu4Au have been probed by magnetic susceptibility, χ(T)χ(T), magnetization, M(μ0H)M(μ0H), and specific heat, Cp(T), measured down to 1.8 K. The low temperature χ(T)χ(T) data shows probably an antiferromagnetic (AFM)-like anomaly associated with a Néel temperature TN=3.9 K. In the paramagnetic region, χ(T)χ(T) data follows the modified Curie–Weiss law with an effective magnetic moment μeff=3.547(5)μBμeff=3.547(5)μB and Weiss temperature θp=−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(μ0H)M(μ0H) 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)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.