TEMPERATURE AND APPLIED VOLTAGE-DEPENDENCE OF MAGNETORESISTANCE RATIOIN FE AL OXIDE FE JUNCTIONS

The tunnel magnetoresistance(TMR) ratio have been investigated in the Fe/Al oxide/Fe junctions, specifically the temperature and applied vol tage dependence of the TMR ratio. It was found that the dependence of resistance at saturation magnetization state (R-s) on the applied volt age at 4.2 K is completely anomalous in terms of the expected tunnelin g behavior. This ''zero-bias anomaly'' is due to the magnetic impurity in or near the boundary between ferromagnetic electrodes and insulato r. The TMR ratio decreased rapidly with increasing temperature. The TM R ratio also decreased when increasing the applied voltage. We discuss ed the dependence of the TMR ratio on temperature acid applied voltage taking into account the impurity assisted tunneling.