Giant oscillations in spin-dependent tunneling resistances as a function of barrier thickness in fully epitaxial magnetic tunnel junctions with a MgO barrier

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Giant oscillations in spin-dependent tunneling resistances as a function of MgO barrier thickness (tMgO) were observed for fully epitaxial magnetic tunnel junctions with Heusler alloy Co2Cr0.6Fe0.4Al electrodes and a MgO barrier. The oscillations in tunneling resistances were well approximated by a superposition of an exponential function of exp(atMgO+b) and a periodic function of 1+C cos[(2π/T)tMgO+φ] with significantly large amplitudes C∼0.16±0.01 even at 293 K for both parallel and antiparallel magnetization orientations. The period was found to be almost independent of temperature and bias voltage (V). The amplitudes C showed only weak dependence on V at least up to 0.2 V. These features should be a key to understand the origin of the pronounced oscillations.
2010-04-27