Proximity exchange coupling across an MgO tunnel barrier detected via spin precession

Proximity exchange coupling across an MgO tunnel barrier is observed up to room temperature. The proximity exchange field, which ferromagnetic Fe exerts on the spin accumulation in a Fe/MgO/Si tunnel contact, modifies the spin precession of the spin accumulation at the MgO/Si interface and is detected via the inverted Hanle effect in a three-terminal configuration. It produces shifts and hysteresis of the inverted Hanle curves, and discontinuities at the coercive field of the ferromagnet, at which the magnetization and thereby the exchange field is reversed. The proximity exchange field is observed not only at low temperature, as we previously reported, but also at room temperature. We compare the magnitude of the exchange field at different temperatures, and complement this with data on the tunnel resistance and the tunnel spin polarization, which was extracted from four-terminal non-local spin transport in the same devices.