AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI-MoA

Paper MI-MoA1
Positive Exchange Bias Model: Fe/FeF@sub 2@ and Fe/MnF@sub 2@ Bilayers

Monday, October 2, 2000, 2:00 pm, Room 206

Session: Thin Films and Multilayers
Presenter: R.D. Portugal, Pontificia Universidad Católica, Chile
Authors: M. Kiwi, Pontificia Universidad Católica, Chile
J. Mejía-López, Pontificia Universidad Católica, Chile
R.D. Portugal, Pontificia Universidad Católica, Chile
R. Ramírez, Pontificia Universidad Católica, Chile
Correspondent: Click to Email
Positive exchange bias (PEB) is a phenomenon that was recently observed experimentally while normal (or negative) exchange bias (NEB) had been discovered more than forty years ago. It is remarkable that both phenomena are observed in the same samples subject to different cooling fields. Here we put forward a model to explain PEB and its crossover to NEB in Fe/FeF@sub 2@ and Fe/MnF@sub 2@ bilayers. Our model incorporates recent experimental information, such as the perpendicular coupling between the ferromagnet (FM) and the antiferromagnet (AFM) and that compensated AFM interfaces show the highest NEB shifts. A freezing of the canted AFM interface spins is proposed, and thus while hysteresis loops are performed the energy is stored in an incomplete domain wall in the FM. Recent polarized neutron reflectometry experiments provide strong support for this picture.@footnote 1@ The energy minima at each point of the magnetization curve are obtained exactly, with arbitrary precision, by a new analytical formulation which is introduced in this work. The results extracted from the model are in qualitative and quantitative agreement with available experimental facts. @FootnoteText@ @footnote 1@ M R Fitzsimmons et al., Phys. Rev. Lett. 84, 3986 (2000).