FERROMAGNETIC RESONANCE IN A TWO BAND FERROMAGNET.
CASE INST OF TECH CLEVELAND OHIO SOLID STATE GROUP
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The classical two band ferromagnetic model is formulated which corresponds to the current quantum mechanical multiple electronic band model. The effective exchange interactions including one electron as well as exchange contributions are introduced as effective exchange fields and the dynamical equations of motion of the magnetization, coupled with Maxwells equations, are solved for ferromagnetic resonance. The solution for a single band ferromagnet has two pairs of modes of the same form as the insulator theory modes, except for the method of calculating the exchange parameters. In addition to the acoustic and electromagnetic pairs of modes corresponding to the single band solutions, the two band ferromagnet has an additional pair of optical modes. The incremental band magnetizations for the optical modes are opposite in direction and tend to cancel. For identical bands cancellation is exact and coupling to the optical mode is not possible. For nonidentical bands, coupling is possible as the cancellation is not complete. For typical parameters of nickel, computer solution gives the dispersion relations and shows a resonance of the right polarized optical mode in the infrared near six microns. Author
- Electricity and Magnetism