Ferromagnetic resonance in exchange spring thin films

The ferromagnetic resonance frequencies have been calculated for a soft/hard Co/CoPt exchange spring thin film system. In this geometry the magnetostatics are crucial to understanding the variation of resonant frequency with field due to the out-of-plane component of magnetization of the CoPt hard layer. When exchange coupling between films exists, significant changes in the resonant frequency occur. For in-plane reverse applied fields, a spiral is formed in the soft Co layer. This appears as a double minimum in the resonant frequency as a function of the in-plane applied field. The positions of the frequency minima correspond to the beginning and end of the spiral formation in the Co layer. The frequency of the maximum provides a sensitive measure of the perpendicular anisotropy in the cobalt film. (C) 2003 American Institute of Physics.