AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeA

Paper MI-WeA8
Magnetic and Structural Properties of Lattice Matched Epitaxial Antiferromagnetic/Ferromagnetic Bilayers

Wednesday, November 17, 2004, 4:20 pm, Room 304A

Session: Exchange Coupling, Surfaces, and Interfaces
Presenter: P. Mani, The University of Alabama
Authors: P. Mani, The University of Alabama
V.V. Krishnamurthy, The University of Alabama
S. Maat, Hitachi Global Storage Technologies
A. Kellock, IBM Research Division
G.J. Mankey, The University of Alabama
Correspondent: Click to Email
The antiferromagnetism of FePt@sub 3@ films grown on Al@sub 2@O@sub 3@(11-20) and MgO(110) has been confirmed by neutron scattering. Fe@sub x@Pt@sub 1-x@ (0.2 < x < 0.3) exhibits antiferromagnetic ordering below 160K depending on the film growth temperature, substrate symmetry and composition of the alloy.@footnote 1@ These FePt@sub 3@ films offer a fascinating route to understand the relationship between structure and magnetism in exchange bias systems since Fe@sub x@Pt@sub 1-x@ grows as an ordered antiferromagnet when deposited at 750°C and as a disordered ferromagnet when deposited at 150°C. In addition, ferromagnetic films of CoPt@sub 3@ have the same lattice constant as FePt@sub 3@. Thus these film systems provide a pathway to create strain-free interfaces to test the current models of exchange bias. Both positive and negative exchange bias were observed in strained Fe/FePt@sub 3@ bilayers with different in-plane cooling field directions.@footnote 2@ In the present study, Fe@sub x@Pt@sub 1-x@ films are grown on MgO(111)and a-axis sapphire by co-sputtering Fe and Pt. Epitaxy and alloy ordering have been confirmed by x-ray diffraction. Rutherford backscattering spectrometry and energy dispersive analysis of x-rays were used to characterize the composition of these alloys, which confirms that stoichiometry can be controlled within a tolerance of 1% in our ultra clean sputtering system. Detailed measurements of the structural and magnetic properties of lattice matched FePt@sub 3@/Fe@sub 0.25@Pt@sub 0.75@ and FePt@sub 3@/CoPt@sub 3@ and their relation to current models of exchange bias behavior will be discussed. @FootnoteText@ @footnote 1@ S. Maat, O. Hellwig, G. Zeltzer et al., Phys. Rev. B, 63, 134426 (2001).@footnote 2@ R.L. Compton, M.J. Pechan, S. Maat, and Eric. E. Fullerton, Phys. Rev. B, 66 (5), 054411 (2002).