Nanoscopic processes of current-induced switching in thin tunnel junctions

In magnetic nanostructures, one usually uses a magnetic field to commute between two resistance (R) states. A less common but technologically more interesting alternative to achieve R-switching is to use an electrical current, preferably of low intensity. Such current-induced switching (CIS) was recently observed in thin magnetic tunnel junctions and attributed to electromigration of atoms into/out of the insulator. Here, we study the CIS, electrical resistance, and magnetoresistance (MR) of thin MnIr/CoFe/AlO_x/CoFe tunnel junctions. The CIS effect at room temperature amounts to 6.9% R-change between the high and low states and is attributed to nanostructural rearrangements of metallic ions in the electrode/barrier interfaces. After switching to the low R-state, some electromigrated ions return to their initial sites through two different energy channels. A low (high) energy barrier of ~0.13 eV (~0.85 eV) was estimated. Ionic electromigration then occurs through two microscopic processes associated with different types of ions sites/defects. Measurements under an external magnetic field showed an additional intermediate R-state due to the simultaneous conjugation of the MR (magnetic) and CIS (structural) effects