Electrical noise in hysteretic ferromagnet-insulator-ferromagnet tunnel junctions

Low frequency noise has been measured in magnetic tunnel junctions that hav e Al2O3 tunnel barriers and magnetoresistance values up to 35% at 295 K. Fl uctuations in voltage were found to cross over from Johnson noise to shot n oise at low bias voltages, in quantitative agreement with theories of noise in quantum ballistic systems. 1/f resistance noise, where f is frequency, predominates at larger biases and is proportional to the mean current squar ed. This noise is attributed to trapping processes and it depends sensitive ly on the relative position of the oxide edge and the ferromagnet-Al interf ace. (C) 1999 American Institute of Physics. [S0003-6951(99)03304-5].