Quantum oscillations of tunneling magnetoresistance in magnetic tunnel junctions

Taking into account a tunneling current with ballistic and diffusive components, we study the tunneling magnetoresistance (MR) in FM/I/NM/I/FM double tunnel junctions where FM is the ferromagnet, NM the normal metal, and I the insulating barrier. The ballistic component results in oscillations of the MR with a single period, while the diffusive one leads to their decay with thickness of the NM layer. It is shown that the experimental results observed in NiFe/Al2O3/Cu/Co junctions by Yuasa, Nagahama, and Suzuki [Science 297, 234 (2002)] are intrinsic features, which can be reproduced by the present calculations.