Inelastic neutron scattering study on crystal field excitations in PrMg₃

We have studied the crystalline-electric-field excitation spectrum in PrMg₃ with non-Kramers doublet Γ₃ ground state by inelastic neutron scattering experiments on powder and single crystal samples. Experimental results have revealed the development of a dispersive structure in the Γ₃-Γ₄ and the Γ₃- Γ₅ excitations below 50 K. Moreover, the excitation spectra of the Γ₃-Γ₄ transition were found out to consist of two peaks, resulting in the two branches in dispersion relation. While one branch shows a relatively strong q-dependence, the other branch is almost dispersionless. The dispersion of the former branch is considered to result from the magnetic dipole exchange interaction, but the origin of the excitation of the latter branch is not clear at present.