Influence of magnetization anisotropy and cell distortion on the crystal field parameters determined on a single crystal of NdAl2

The isothermal magnetization of a NdAl2 single crystal has been measured at 4.2 K, along the main symmetry directions in static fields up to 150 kG. In this ferromagnetically ordered compound, [100] is the easy direction of magnetization and [111] the hard direction. Taking into account the tetragonal distortion observed along the [100] direction an effective crystal field Hamiltonian is derived and values are obtained for the crystal field parameters of second, fourth, and sixth order. The effects of the distortion on the energy and on the magnetization anisotropy are computed. The comparison between the measured and calculated magnetization values along [111] allows to analyse the process of magnetization in this direction.