Proximity exchange coupling in a Fe/MgO/Si tunnel contact detected by the inverted Hanle effect

A ferromagnet is shown to exert an exchange field on the spin accumulation localized in the semiconductor interface region of a Fe/MgO/Si tunnel contact. The proximity exchange coupling across the MgO modifies spin precession of the spin accumulation and thereby produces detectable signatures in the inverted Hanle effect: exchange-induced shifts of the inverted Hanle curves, hysteresis, and discontinuities at the coercive field of the ferromagnet, at which the exchange field is reversed. The proximity exchange field is locked antiparallel to the magnetization of the ferromagnet, has values up to 380 Oe, and can be controlled by a bias voltage across the tunnel contact.