Diode effect in magnetic tunnel junctions with impurities

The influence on the I-V characteristics and tunnel magnetoresistance (TMR) of impurities embedded into the insulating barrier (I) separating the two ferromagnetic electrodes (F) of a magnetic tunnel junction was theoretically investigated. When the energy of the electron bound state at the impurity site is close to the Fermi energy, the current and TMR are strongly enhanced in the vicinity of the impurity. If the position of the impurity inside the barrier is asymmetric, e.g., closer to one of the F∕I interfaces, the I-V characteristic exhibits a quasidiode behavior. The cases of a single impurity and of a planar random distribution of impurities were both studied.