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Abstract:
Inelastic neutron scattering (INS) experiments and random phase
approximation calculations have been used to investigate the low energy
spin wave excitations in PrNi2Si2. The modulated magnitude of the
ordered magnetic moments of Pr3+ ions implies that the associate,
longitudinally polarized magnetic excitations are more intense and
dispersive than the usual transverse spin waves. Within the random phase
approximation the results are in good overall agreement with the
predictions made by the model determined previously from the
paramagnetic excitations. The most unusual observation is the well
defined amplitude mode detected close to the magnetic Bragg point
existing simultaneously with the phason mode. At low energies, an extra
mode is observed to hybridize with the magnetic phasons in the
neighborhood of the magnetic Brillouin zone center. A magnetoelastic
interaction between the magnetic excitations and the longitudinal
phonons is able to explain part of the disturbances, but it is concluded
that the extra mode must be of some other, unknown origin.
