Thermally activated magnetization reversal in magnetic tunnel junctions

In this paper, the magnetization reversal of the ferromagneticlayers in the IrMn/CoFe/AlO_x/CoFe magnetic tunnel junction hasbeen investigated using bulk magnetometry. The films exhibit verycomplex magnetization processes and reversal mechanism. Thermalactivation phenomena such as the training effect, the asymmetry ofreversal, the loop broadening and the decrease of exchange fieldwhile holding the film at negative saturation have been observed onthe hysteresis loops of the pinned ferromagnetic layer while not onthose of the free ferromagnetic layer. The thermal activationphenomena observed can be explained by the model of two energybarrier distributions with different time constants.