Anomalous behaviour of temperature and bias-voltage dependence of tunnel-type giant magnetoresistance in insulating granular systems

The temperature and bias-voltage dependence of tunnel-type giant magnetoresistance (MR) in insulating granular films Co-A1-0. At low temperatures, enhancement of MR larger than the theoretical value, was observed, decreasing sharply with increasing temperature. MR did not decrease with rising bias voltage. The effect of temperature was different from that of bias voltage.