Nonlinear power dependence of ferromagnetic resonance in NiFe/Pt/CoFeB trilayer.

The static and dynamic magnetization properties for a NiFe/Pt/CoFeB tri-layered film have been investigated. We find that the two ferromagnetic layers separated by a Pt spacer are ferromagnetically coupled even at room temperature. Moreover, the damping constant for the NiFe layer is found to show the significant enhancement with non-linear power dependence. These unique magnetic features observed in the NiFe layer can be understood by the weak ferromagnetism induced in the Pt spacer between two ferromagnetic layers.