Exact formulation for axial spinwave propagation in a constant magnetic-field gradient

The differential equation is solved for the magnetisation of a lossfree one-dimensional spinwave packet, travelling under a constant magnetostatic-field gradient, in a single-crystal ferrimagnetic. Expressions are derived for the stored energy, power flux, phase and energy velocities and time delay. The asymptotic time delay is compared with the harmonic-wave approximation, and it is concluded that for rod geometries the greatest deviation occurs close to the end face.