@article{a708998ad7d44424ba04b25c47b3dd1f,
title = "Translational-mode dynamics of exchange-biased vortices",
abstract = "Recent investigations of magnetic vortices in ferromagnetic (FM)antiferromagnetic bilayer circular dots show that a magnetic vortex pattern can be imprinted in the antiferromagnet when the bilayers are cooled through the blocking temperature of the system after setting the magnetic state in the FM. Here we investigate the effects of the patterned pinning profile on the magnetization dynamics of these exchange-biased magnetic vortices. A magnetic vortex in a micron-sized magnetically soft element exhibits a low-frequency translational dynamic mode and, since the frequency of this mode is defined by the shape of the energy profile of a displaced vortex, the addition of a vortex-shaped pinning-field profile should influence its motion. Micromagnetic simulations show that the frequency scales linearly with the magnitude of the local pinning field. In a 500 nm permalloy dot, 15 nm thick, a more than twofold increase in the frequency is expected for experimentally realizable exchange-bias fields.",
author = "Buchanan, {K. S.} and A. Hoffmann and V. Novosad and Bader, {S. D.}",
note = "Funding Information: We thank F. Fradin, S.-H. Chung, J. Sort, and J. Nogues for helpful discussions. Work at Argonne, including use of facilities at the Center for Nanoscale Materials, was supported by the U.S. Department of Energy, under Contract No. DE-AC02-06CH11357. FIG. 1. (a) Calculated spin distribution of a magnetic vortex in a 500 - nm diameter, 15 - nm thick circular dot of permalloy. To represent the effects of field cooling at remanence, a pinning field in the shape of a vortex, including the core, is imposed. (b) Oscillations of the vortex magnetization as a function of time with and without a local pinning field of H ex = 90 Oe after removing a perturbation field of h x = 10 Oe . FIG. 2. Vortex translational-mode (a) frequency and (b) amplitude as a function of local exchange-bias field magnitude H ex obtained from micromagnetic simulations of a 500 - nm diameter, 15 - nm thick circular dot of permalloy with a vortex-shaped pinning field [Fig. 1(a) ]. Perturbation field h x = 10 Oe . FIG. 3. Dynamic simulation results for a 1 μ m Py dot, 12 nm thick, with and without a vortex-shaped pinning field of H ex = 90 Oe . (a) Frequency ν , (b) baseline magnetization M x 0 ∕ M s , (c) amplitude M x ∕ M s , and (d) orbital ellipticity M x ∕ M y are shown as a function of static field H . Perturbation field h x = 25 Oe . ",
year = "2008",
doi = "10.1063/1.2830643",
language = "English (US)",
volume = "103",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "7",
}