Magnetic properties of the orthorhombic NdPd

The equiatomic NdPd compound crystallizes in the orthorhombic CrB structure type ( oS 8, Cmcm , No. 63). The NdPd phase melts congruently at 1240 °C, as observed by differential thermal analysis; one further sharp thermal effect detected at 1040 °C is very likely due to a structural transition. We confirm the CrB prototype for the low-temperature form of NdPd. The lattice parameters of this compound are a =3.842(2) A, b =10.776(7) A, c =4.605(2) A, as obtained from Guinier powder pattern; those for the corresponding iso-structural LaPd compound, prepared as non-magnetic reference, are a =3.947(2) A, b =11.036(3) A, c =4.663(2) A. Despite the fact that NdPd has been known since long, its physical properties have not been investigated till date. Here we report the results of magnetization, heat capacity and electrical resistivity measurements performed on this compound. NdPd undergoes a single ferromagnetic transition close to 15 K, inferred from a sharp upturn in the magnetization at lower temperatures and from Arrott plots measured at selected temperatures between 1.9 and 18 K. The coercive field and remnant magnetization at 1.9 K are 320 Oe and 0.24 μ B /f.u., which become negligible at 15 K. A sharp peak in the heat capacity at ≈15 K confirms the bulk magnetic transition. Isothermal magnetization at 2 K shows a tendency to saturation, reaching a value of 1.9 μ B /f.u. at the maximum applied field of 70 kOe. The zero field resistivity shows an anomaly near 15 K, in correspondence with the magnetic and heat capacity data. A negative magnetoresistivity, typical of a ferromagnet, is observed in the magnetically ordered state in an applied magnetic field of 50 kOe. LaPd is a typical Pauli paramagnet with a Sommerfeld coefficient γ =3.9 mJ/mol K 2 .