Current driven resistance changes in low resistance x area magnetic tunnel junctions with ultra-thin Al-Ox barriers

Current induced resistance changes were investigated in magnetic tunnel junctions with ultrathin Al-O-x barriers. The nonuniformity of the insulator induced a strong coupling between the two magnetic electrodes and no magnetoresistance. However, the current-voltage (I-V) characteristics at low bias voltages were consistent with a tunnellike behavior. At larger bias voltages, they showed an abrupt change of slope that was reversible for an opposite voltage polarity. The resistance versus current (R-I) curves exhibited reversible resistance changes that reached over 100%. We interpret this as controlled electromigration in local nanoconstrictions of the barrier. (C) 2004 American Institute of Physics.