PUB - Publikationen an der Universität Bielefeld

Tunnel magnetoresistance curves were measured in very small tunnel junctions from scales of I Am to 50 nm using conductive atomic force microscopy. The junction arrays were prepared by a simple fabrication process using electron beam lithography. In large size junctions, the minor loops shifted in the negative field direction corresponding to ferromagnetic coupling between free and pinned layers. With decreasing size, the shift changed to the positive field direction corresponding to antiparallel coupling. The dependence of the shift was quantitatively explained by a model taking account of both Neel-type and dipole coupling. The minor loops showed asymmetric shape depending on field sweep directions. (C) 2003 American Institute of Physics.