Spin tunneling in Ni–Fe/Al2O3/Co junction devices (invited)

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Abstract
Magnetoresistive properties of a Ni–Fe/Al–oxide/Co junction with various junction area between 3.5×3.5 μm2 and 85×85 μm2 have been studied. Antiferromagnetic interlayer exchange coupling between magnetic electrodes, which was predicted theoretically by Slonczewski was found experimentally. The antiferromagnetic exchange coupling strength increased with reduction of the junction area. The tunneling magnetoresistive effect tends to increase with reduction of the junction area. However, it was much smaller than the tunneling magnetoresistance ratio expected from the spin polarizations of electrodes. The reasons were discussed briefly.