A mechanism for the large magnetoresistance observed recently in Co-Al-O granular magnetic films is presented. It is shown that the resistivity decreases with increasing applied magnetic field because the spin-dependent tunneling increases as the relative orientation of the magnetization between grains becomes parallel. With this mechanism we are able to account for the dependence of the magnetoresistance on the magnetization and temperature.

• Received 7 August 1995

DOI:https://doi.org/10.1103/PhysRevB.53.R11927