Magnetic excitations in single crystal PrNiSn

Inelastic neutron scattering results from a single crystal of the rare earth intermetallic PrNiSn are presented. Crystalline electric field excitations are found at 0.5, 2.4 and around 3.5 meV. The lower modes show little dispersion over q, but the 3.5 meV splits into two excitations, most clearly seen along the c* direction. Fitting the modes with gaussian functions allows us to show the pronounced dispersion to be of the form E(q)=E0+J1cos(qπ) for the upper mode, and E(q)=E0+J1cos(qπ)+J2cos(2qπ) for the lower mode. This suggests a longer range interaction for the lower mode. The lowest excitation at 0.5 meV confirms predictions made from previous measurements on polycrystalline samples that indicate a low lying CEF level.