Proximity influence of a ferromagnet on the magnetoresistance of Cr film across a nonmagnetic layer

(5 nm) Cr (100)/( x nm) MgO (100)/(30 nm) Fe3O4 (100) (1 < x < 6 nm), as well as (5 nm) Cr (100)/(5 nm) MgO (10 0) structures were grown on MgO (10 0) substrates using molecular beam epitaxy. The proximity influence of the Fe3O4 bottom layer on the in-plane transport and magnetotransport properties of the Cr layer was studied. A reversal of the magneto resistance (MR) sign in the Cr film was observed for MgO layer thickness less than or equal to 5 nm. The thickness of the MgO layer at which the proximity influence of the Fe3O4 on the MR of the Cr film is still observed is too large to be accounted for by an exchange interaction. Our results suggest that the magnetic structure in the Cr film adjoining a pinhole in the MgO layer is distorted due to the exchange coupling. Such areas in the Cr film are thought to contribute to the negative MR. (C) 2004 Elsevier B.V. All rights reserved.