Abstract
We have performed inelastic magnetic neutron scattering experiments on and in order to study the Nd -spin dynamics at low energies In all samples we find at high temperatures a quasielastic line (Lorentzian) with a linewidth which decreases on lowering the temperature. The temperature dependence of the quasielastic linewidth can be explained with an Orbach process, i.e., a relaxation via the coupling between crystal field excitations and phonons. At low temperatures the magnetic response correlates with the electronic properties of the layers. In the insulator the quasielastic line vanishes below 80 K and an inelastic excitation occurs. This directly indicates the splitting of the ground state Kramers doublet due to the static antiferromagnetic order of the Cu moments. In with and with superconductivity is strongly suppressed. In these compounds we observe a temperature independent broad quasielastic line of Gaussian shape below This suggests a distribution of various internal fields on different Nd sites and is interpreted in the frame of the stripe model. In such a quasielastic broadening is not observed even at lowest temperature.
- Received 17 March 1999
DOI:https://doi.org/10.1103/PhysRevB.60.9793
©1999 American Physical Society