Abstract
A systematic Brillouin light scattering (BLS) study on long-wavelength spin waves (SWs) in ferromagnetic TM–Al–O (TM=Co, Fe) nano-granular films with thickness of >1 µm was performed under magnetic fields of up to 4 kOe at room temperature. BLS spectra consist of a pair of bulk SW peaks on both frequency sides and a surface localized SW peak only on the positive frequency side in this study. These SW frequencies as a function of the magnetic field can be fully reproduced by the magnetostatic frequency formula developed for a semi-infinite uniform ferromagnetic medium with an exchange coupling and an in-plane uniaxial magnetic anisotropy. We determined a set of the magnetic constants including the exchange field H E for each film. Combining the exchange field H E with the electrical resistivity ρ for each film at room temperature, we found an inverse-square law given by ρ= a ( H E ) -2 for both the Co and Fe granular films with a Fe =30.3 µΩ·cm·(kOe) 2 and a Co =22.1 µΩ·cm·(kOe) 2 , respectively.
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