High frequency permeability of patterned spin valve type thin films

The dynamic response of spin valve films were studied and compared to NiFe/CoFe bilayer and NiFe single layer films by measuring their high frequency permeability spectra on sheet and patterned samples. It was found that the high frequency response of these thin films were affected only by the ferromagnetic resonance and the behavior was well described by the calculated Landau-Lifshitz-Gilbert permeability. The resonance frequency of spin valve films was strongly influenced by the interaction field from the pinned layer. Decreasing interlayer thickness of Cu resulted in an increase of the interaction field, which shifted the resonance frequency to higher frequencies while reducing the initial permeability. The shape anisotropy, which was increased by decreasing pattern size, also shifted the films resonance frequency to higher values accompanied by lowered initial permeabilities. Regarding their dynamic response, spin valve films were found to be suitable for ultrahigh recording densities, when the effective anisotropy was sufficiently large. (C) 1999 American Institute of Physics. [S0021-8979(99)71908-0].