AVS 45th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Thursday Sessions
       Session MI-ThP

Paper MI-ThP5
Minor Loops in a Bimodal Magneto-Optical Medium

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Magnetic Interfaces and Nanostructures Poster Session
Presenter: R.A. Fry, The George Washington University
Authors: R.A. Fry, The George Washington University
L.A. Bennett, The George Washington University
E. Della Torre, The George Washington University
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Bimodal magnetic behavior was recently encountered in a (0.3nm Co/1.2nm Pt)@sub 15@ multilayer magnetic film with perpendicular magnetization by using an automated magneto-optical Kerr effect (MOKE) magnetometer.@footnote 1@ In the two separate magnetic transitions, differences in the ratio of the Kerr rotation to ellipticity were noted. To explain this behavior, it was postulated that there are two different magnetic entities (layers) in this material, each with a characteristic switching field, Kerr rotation, and Kerr ellipticity. To further investigate the magnetization behavior in this material, including magnetic exchange interactions between the two magnetic species, a series of minor loop experiments was performed. From the major loop data, two critical switching field values were observed, H@sub K1@ and H@sub K2@, where H@sub K1@ > H@sub K2@. H@sub K1@ is the smallest reversal field required to fully saturate the material, and H@sub K2@ is the field at which the observed step in the loop occurs. From the minor loops, a third critical field is identified as H@sub K3@. The observed magneto-optical behavior can be explained by defining two interacting magnetic entities, A and B, with intrinsic coercivities, H@sub A@ and H@sub B@. H@sub K1@ is the sum of H@sub A@ and the interaction field (H@sub i@); H@sub K2@ is the sum of H@sub B@ and H@sub i@; and, H@sub K3@ is the sum of -H@sub B@ and H@sub i@. The height of the minor loop is directly related to where on the major loop the reversal is initiated. By using minor loop MO measurements, the observed bimodal magnetization behavior was decomposed into two individual loops which are mutually interacting. From this decomposition, the intrinsic coercivities of the individual magnetic entities, as well as the interaction field between them, was obtained. This paper presents the experimental data and the excellent fit to this proposed model. We thank Dr. R.F.C. Farrow for providing these samples and N.I.S.T. for financial support. @FootnoteText@ @footnote 1@R.A. Fry, L.H. Bennett, E. Della Torre, R.D. Shull, W.F. Egelhoff, Jr., R.F.C. Farrow, and C.H. Lee, to be presented at Seventh International Conference on Magnetic Recording, (1998)