Thermally stable MnIr based spin valve type tunnel junction with nano-oxide layer over 400 °C

We have investigated the annealing effect of magnetic tunnel junctions (MTJs) with or without nano-oxide layer (NOL). For MTJ without NOL, TMR ratio increased up to 300 °C and the highest value was 21.6%. On the other hand, TMR ratio of MTJ with NOL increased up to 400 °C and the highest value was 22.7%. As shown in the auger electron spectroscopy (AES) and transmission electron microscopy (TEM) results, this improved thermal stability is due to NOL in the pinned layer. Mn diffusion into Al–O barrier is blocked and interface of Al–O is smothered by NOL. These may be the main reasons of high thermal stability of MTJ with NOL.