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

Paper MI-MoA2
Asymetry of Magnetization Reversal in the Fe/(Fe,Mn)F@sub 2@ Exchange Bias System as a Function of Crystallinity

Monday, October 2, 2000, 2:20 pm, Room 206

Session: Thin Films and Multilayers
Presenter: A. Hoffmann, Los Alamos National Laboratory
Authors: A. Hoffmann, Los Alamos National Laboratory
M.R. Fitzsimmons, Los Alamos National Laboratory
C. Leighton, University of California, San Diego
K. Liu, University of California, San Diego
I.K. Schuller, University of California, San Diego
J. Nogués, Universitat Autònoma de Barcelona, Spain
C.F. Majkrzak, National Institute of Standards and Technology
J.A. Dura, National Institute of Standards and Technology
H. Fritzsche, Hahn-Meitner Institut, Berlin, Germany
Correspondent: Click to Email
Using polarized neutron reflectometry we have recently shown that the magnetization reversal can be different on both sides of the hysteresis loop for polycrystalline Fe exchange coupled to epitaxial twinned FeF@sub 2@ or MnF@sub 2@.@footnote 1@ Namely, with decreasing field (+M@sub s@ -> -M@sub s@) we observe a rotation of the magnetization indicated by the presence of spin-flip scattering, while for increasing field (-M@sub s@ -> +M@sub s@) the data suggest magnetization reversal by domain wall motion. However for epitaxial twinned films of FeF@sub 2@ and MnF@sub 2@, this difference of magnetization reversal depends on the direction of the cooling field with respect to the crystallographic orientation. In order to clarify the role of frustration between twinned antiferromagnetic domains, we examined the asymmetry of the magnetization reversal also in samples with either single-crystal (untwinned) or (110) textured polycrystalline FeF@sub 2@ films. In untwinned and textured samples we detected no significant asymmetry in the magnetization reversal. This suggests that the twinning of the antiferromagnet is essential for the asymmetry in the magnetization reversal to occur. This can be understood by a "45 degree coupling" of the Fe to the FeF@sub 2@ due to a twin-driven frustration. As a result there can be a unidirectional anisotropy due to exchange bias along the easy axis of the ferromagnet, which in turn then may give rise to the asymmetry in the magnetization reversal. This work was supported by U.S. Department of Energy, BES-DMS under Contract No. W-7405-Eng-36, grant DE-FG03-87ER-45332, and funds from the University of California Collaborative University and Laboratory Assisted Research. @FootnoteText@ @footnote 1@ M.R. Fitzsimmons, P. Yashar, C. Leighton, I.K. Schuller, J. Nogués, C.F. Maikrzak, and J.A. Dura, Phys. Rev. Lett. vol. 84, 3986 (2000).