Thermally stable MnIr based spin valve type tunnel junction with nano-oxide layer over 400 deg. 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 deg. C and the highest value was 21.6%. On the other hand, TMR ratio of MTJ with NOL increased up to 400 deg. 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