We calculate the spin-transfer torque in Fe/MgO/Fe tunnel junctions and analyze the results in comparison to all-metallic junctions. We show that the spin-transfer torque is interfacial in the ferromagnetic layer to a greater degree than in spin-valve systems. This result originates in the half metallic behavior of Fe for the Δ sub 1 states at the Brillouin zone center; in contrast to all-metallic structures dephasing does not play an important role. We further show that it is possible to get a component of the torque that is out of the plane of the magnetizations and which is linear in the bias. However, observation of such a torque requires highly ideal samples.
Citation: Physical Review Letters
Pub Type: Journals
electronic structure, Fe/MgO/Fe, magnetic random access memory, magnetotransport, spin transfer torque, tunnel junctions