Magnetoresistance of amorphous ferromagnetic metals

Amorphous ferromagnetic films of NiAu and and Co are prepared by quenched condensation onto a substrate at He temperature. Amorphous ferromagnetic metals are particularly well suited to investigate the influence of an external magnetic field in the ferromagnetic state on the transport properties. The small mean free path of the conduction electrons suppresses the complications of the band structure and its consequences on the transport properties. The magnetoresistance is measured in an external field up to 80 kG. $\frac{d\rho }{dB}$ is negative and takes values up to 2 × ${10}^{-9\mathrm{}}$ ${\mathrm{m}}^3$/Asec. The results are discussed within the band model of ferromagnetism. They contradict the rigid-band model for NiAu alloys. Within the Heisenberg model the influence of anisotropy fields on the resistivity again yields values for $\frac{d\rho }{dB}$ which are too small.