Structural, magnetic, electronic and transport properties of NdCu₂

Abstract

NdCu2 crystallizes in the orthorhombic CeCu2 structure. Using temperature dependent X-ray diffraction the variations of the lattice parameters with temperature have been measured and compared with those of YCu2. A magnetic ordering temperature at TN=6.5+or-0.1 K and a spin-reorientation temperature (TR=4.1+or-0.1 K) have been observed in the susceptibility, specific heat and resistivity. Further field-induced magnetic transitions around 1, 3 and 15 T (depending on the measuring temperature) were found in the magnetization and magnetoresistance. A preliminary magnetic phase diagram of NdCu2 is presented. The crystal field excitation temperatures determined by inelastic neutron scattering experiments are E1/kB=34 K, E2/kB=58 K, E3/kB=84 K and E4/kB=164 K. For the determination of the nine crystal field parameters Vlm the superposition model has been applied. The deduced set of parameters was used to calculate the crystal field influence on the magnetization, specific heat, thermal expansion and electrical resistivity. From an analysis of the X-ray powder diffraction data the lattice constants a=4.3844 AA, b=7.0350 AA and c=7.4186 AA and the atomic positional parameters (yCu=0.0506, zCu=0.1659, zNd=0.5383) inside the unit cell were obtained.