Transport and Magnetic Properties of Ferromagnetic Co–Al–O and Fe–Al–O Granular Films

We investigate the transport and magnetic properties of ferromagnetic Fe–Al–O and Co–Al–O granular films. A negative linear magnetoresistivity is found at least up to 27 T for Co–Al–O films. The temperature dependence of the magnetization of Fe–Al–O films can be explained in terms of the T1.5-law for three dimensional spin waves theory, but that of Co–Al–O films does not obey the simple power law expected from this theory. The coercive field of a Co–Al–O film is strongly dependent on temperature.