Oscillatory interlayer exchange coupling in [Pt/Co]_n/NiO/[Co/Pt]_n multilayers with perpendicular anisotropy: Dependence on NiO and Pt layer thicknesses

Authors

Z. Y. Liu, University of Nebraska - Lincoln
Lanping Yue, University of Nebraska-LincolnFollow
D. J. Keavney, Advanced Photon Source, Argonne National Lab, Argonne, Illinois
Shireen Adenwalla, University of Nebraska-LincolnFollow

Date of this Version

12-17-2004

Comments

Published in Physical Review B, 70, 224423 (17 December 2004)
Copyright © 2004 The American Physical Society. Used by permission
URL: http://link.aps.org/abstract/PRB/v70/e224423
doi:10.1103/PhysRevB.70.224423

Abstract

Interlayer exchange coupling has been studied in a series of [Pt( t_Pt Å)/Co(4 Å)]n/NiO( t_NiO)/[Co(4 Å)/Pt( t_Pt Å)]_n multilayers with perpendicular anisotropy. The coupling oscillates between antiferromagnetic and ferromagnetic as a function of t_NiO with a period of ~5 Å, and the oscillatory behavior is related to the antiferromagnetic ordering of the NiO layer. This interlayer coupling between two Co/Pt multilayers is shown to occur domain by domain by magnetic force microscopy imaging. For the strongest antiferromagnetic coupling at t_NiO = 11 Å, an oscillation with a period of ~6 Å is superposed onto the exponential decay of the coupling strength as a function of t_Pt. The exponential decay with t_Pt is ascribed to the exponential decay of the coupling between the Co layers across the Pt layers in each Co/Pt multilayer, and the superposed oscillatory behavior can be attributed to multiple reflections of electron waves at the Co/Pt interfaces and their interference. A linear dependence of the antiferromagnetic coupling strength on 1/n, (where n is the number of repeats), is suggestive of a surface interaction for this interlayer coupling.