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Phys. Rev. B 71, 220409(R) (2005) [4 pages]

Picosecond magnetization dynamics in nanomagnets: Crossover to nonuniform precession

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V. V. Kruglyak*, A. Barman, and R. J. Hicken
School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, United Kingdom

J. R. Childress and J. A. Katine
Hitachi Global Storage Technologies, San Jose Research Center, 650 Harry Road, San Jose, California 95120, USA

Received 26 April 2005; published 27 June 2005

The picosecond magnetization dynamics of arrays of square Ni88Fe12∕Co80Fe20 bilayer nanoelements were studied by optical pump-probe measurements. Experimentally observed modes were found to fall upon two branches, with a crossover from the high- to low-frequency regime as the element size was reduced to less than 220 nm. Micromagnetic simulations revealed that the branches are associated with center and edge modes. The edge mode is found to dominate as the element size is reduced so that the magnetic response to a pulsed field becomes less spatially uniform.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.71.220409
DOI:
10.1103/PhysRevB.71.220409
PACS:
75.40.Gb, 75.30.Ds, 75.50.Ss, 78.47.+p

*Email address: v.v.kruglyak@exeter.ac.uk

Email address: r.j.hicken@exeter.ac.uk