Normal mode formulation of spin wave—Helicon wave interactions in ferromagnetic semiconductors

The linear interactions between spin waves and (drifted) helicon waves in p-type ferromagnetic semiconductors are analyzed in terms of the spatial normal modes of the uncoupled system. The coupled mode equations are investigated in the region of phase synchronism between the negative-energy-carrying helicon mode and the positive-energy-carrying spin wave mode. If these modes are weakly coupled, a convective instability is indicated when the carrier plasma frequency ωpis less than the spin precession frequency ωo.