Spin waves in itinerant multiple-spin-density-wave systems. II

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Abstract
For pt.I see ibid., vol.17, no.5, p.1175 (1987). The spin wave energies and widths for linear- (LSDW) and multiple-spin-density-wave (MSDW) systems are calculated using the formalism developed in pt.I for an itinerant model. Calculations were made for the wave-vector q parallel and perpendicular to the magnetisation in the LSDW state; the velocities near the zone centre were found to depend on the direction of approach to the zone centre and the widths appear to be linear in q for the parallel case but non-linear in the perpendicular case. Three acoustic branches were found for the triple-spin-density-wave case. The widths for these were found to be linear in q. There is a fourth spin wave that plays a vital role in transitions from one MSDW state to another. The authors discuss the nature of these spin-orientation phase transitions and how they can be recognised in the inelastic scattering cross section. The softening of the shear elastic constant is shown to be consistent with the onset of such transitions. Finally, it is conjectured that the orthorhombic phase in the Mn-Ni alloy phase diagram may be accounted for by a MSDW state.

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