AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThA

Paper MI-ThA1
Ultrafast MOKE Study of Magnetization Dynamics in Exchange-Biased FeMn/Co and IrMn/Co Thin Films

Thursday, November 6, 2003, 2:00 pm, Room 316

Session: Magnetization Dynamics
Presenter: K. Seu, College of William and Mary
Authors: K. Seu, College of William and Mary
H. Huang, College of William and Mary
A.C. Reilly, College of William and Mary
W.F. Egelhoff, National Institute of Standards and Technology
L Gan, National Institute of Standards and Technology
Correspondent: Click to Email
We have observed coherent magnetization rotation in exchange-biased Co systems by ultrafast laser pump-probe magnetooptical Kerr effect (MOKE). This technique, first introduced by Ju et al. in the study of NiO/NiFe, uses ultrafast photoexcitation to spontaneously decouple the antiferromagnetic/ferromagnetic system.@footnote 1@ The magnetization undergoes coherent precession as described by the Landau-Lifshitz-Gilbert equations of motion.@footnote 1@ Such ultrafast measurements provide opportunity to study the ultimate time scale for these processes as well as determination of fundamental parameters such as anisotropy and damping.@footnote 2@ This is in analogy with FMR, but with the benefit of direct access to the time domain, sub-micron spatial resolution and straightforward in-situ application. Co exchange-biased systems such as FeMn/Co and IrMn/Co, besides being technologically important, offer an interesting comparison to the NiFe systems. It has been observed that magnetization reversal takes place via more complicated processes in Co, involving nucleation of many small domains.@footnote 3@ Also, recent FMR experiments suggest that the damping in IrMn/Co films is not strongly dependent on exchange bias field strength, unlike the NiO/NiFe system.@footnote 4@ We will present measurements of anisotropy and damping parameters in FeMn/Co and IrMn/Co as a function of Co thickness and exchange bias field strength. These will be used to further explore the nature of exchange biasing in these systems as well as investigate the wider applicability of ultrafast optical techniques. @FootnoteText@ @footnote 1@Ganping Ju et al., Phys Rev Lett 82, 3705 (1999), Phys Rev. B., 62, 1171 (2000)@footnote 2@ M. van Kampen et al., Phys. Rev. Lett. 88, 227201 (2002)@footnote 3@ Chan-Gyu Lee et al., J. Appl. Phys. 91, 8566 (2002)@footnote 4@ R.D. McMichael et al., J. Appl. Phys. 83, 7037 (1998).