Experimental evidence of dipolar interaction in bilayer nanocomposite magnets

We use magnetic thin film hard/non/soft-magnetic trilayer systems to probe the nature of the hard–soft phase interaction and the role played by dipolar fields in onedimensional (d) magnetic systems. We have systematically A.J. Zambano ( ) · H. Oguchi · I. Takeuchi Department of Materials Science and Engineering, and Center for Superconductivity Research, University of Maryland, College Park, MD 20742, USA e-mail: [email protected] Fax: +1-301-3142029 H. Oguchi e-mail: [email protected] I. Takeuchi e-mail: [email protected] J.P. Liu Department of Physics, University of Texas at Arlington, Arlington, TX 76019, USA e-mail: [email protected] Fax: +1-817-2723637 S.E. Lofland Department of Physics, Rowan University, Glassboro, NJ 08028, USA e-mail: [email protected] Fax: +1-856-2564478 L.A. Bendersky National Institute of Standards and Technology, Gaithersburg, MD 20899, USA e-mail: [email protected] Fax: +1-301-9754553 Y. Liu · Z.L. Wang Georgia Institute of Technology, Atlanta, GA 30332-062, USA Z.L. Wang e-mail: [email protected] Fax: +1-404-8949140 investigated six wedge samples where the thickness of a Cu spacer layer (tCu) was gradually changed to create a varying interfacial effect on the interaction between a CoPt hard layer and a Fe soft layer. Magneto-optical Kerr effect was used to obtain the magnetization loops at 28 points on each sample, and the nucleation field (HN) as a function of tCu was employed to characterize the layer interaction as a function of tCu. HN(tCu) show a RKKY oscillatory behavior in addition to a non-negligible dipolar contribution, which had an exponential dependence. The dipolar term, which cannot be always neglected, is affected by the interface roughness and also by the CoPt crystallinity. Therefore, we cannot always consider exchange coupling to be the dominant interaction in one-d hard–soft magnetic bilayer systems, particularly, during magnetic reversal.