New Explanation of the Spin-Wave-Like Excitations in Ni aboveTc

Abstract
A simple paramagnetic scattering function for neutrons, with Lorentzian shapes both in energy and in momentum transfer, is demonstrated to give a full explanation of the spin-wave-like peaks observed in Ni at and above Tc in constant-energy scans of thermal neutron scattering. A model calculation for Ni confirms the direct connection to the critical scattering, and a comparison with EuO reveals that the spectral shape is governed by the spin-diffusion and spin-wave-stiffness constants.