Inelastic neutron magnetic excitons

This energy separation has also been derived from inelastic neutron scattering determinations of the magnetic excitation spectrum of Pr. The excitations in a singlet ground state system are known as magnetic excitons and their dispersion is given by... 

The situation is different if an external field or molecular field is present. In that case Re wl d((D) 0 and there can be considerable hybridization between the phonon like and magnetic exciton-like branches. The excitation spectrum is found from the poles of D q,external field. This behavior seems to be the explanation for the inelastic neutron scattering results found in Pr when a magnetic field was applied (Houmann et al., 1975 Jensen, 1976). 

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