Polarized neutron measurement of ’’forbidden magnon scattering’’ in nickel

Abstract

We have performed inelastic neutron scattering on a Ni⁶⁰ single crystal using neutrons polarized along and against the scattering vector and magnetic field direction. For temperatures above 0.9 T_C we observe magnon stokes (antistokes) scattering for neutrons polarized along (opposite) the magnetization direction. The occurrence of such scattering, which is forbidden at zero temperature, is in disagreement with the conventional Stoner theory of magnetism in metals based on the RPA, but is in qualitative agreement with theories put forward by Korenman, Murray and Prange, Sokoloff, and others.