Thermoelectric Power and Hall Effect in Co–Al–O Granular Films

Abstract

We have measured the thermoelectric power and Hall effect on three Co–Al–O granular films whose conduction mechanism varies from metallic to tunneling type depending on O content. We obtained a finite thermoelectric power (TEP) which decreases with increasing resistivity. In the tunneling type sample, a large field dependence of TEP correlated with the magnetoresistance has been observed. The Hall coefficient of Co–Al–O decreases with increasing sample resistivity, in contrast with the giant Hall effect reported for Ni–SiO 2 granular sample with a similar resistivity. The dominant electronic conduction mechanisms are found to be different between the giant magnetoresistance and the giant Hall effect in ferromagnetic-metal-oxide granular systems.