A high resolution neutron scattering study of single crystal neodymium

It is well known that neodymium develops a modulated antiferromagnetic structure below a first-order transition at T N = 19.9 K. In marked contrast to the other lanthanide metals, no well-defined magnetic excitations have previously been observed in Nd, either in the paramagnetic or magnetically ordered phases. A careful study of the inelastic scattering of neutrons from a new large single crystal of Nd (grown by the solid state electrotransport technique) has been carried out at the Institut Laue-Langevin. Quasielastic scattering which varies markedly with both wavevector and temperature has been found. This scattering has a maximum intensity around T N and exhibits a characteristic linewidth of some 0.4 meV. These results may be interpreted in terms of heavily-damped excitations within low-lying crystal field levels. At lower temperatures, and further from the satellite wavevectors, two weak but well-defined magnetic excitations have been observed.