Precessional dynamics in microarrays of nanomagnets

Copyright © 2005 American Institute of PhysicsTime resolved scanning Kerr microscopy has been used to study the response of square Ni88Fe12/Co80Fe20 bilayer elements to a pulsed magnetic field. Measurements were performed upon a square element of 6000 nm size and upon 64, 120, 220, 425, and 630 nm square elements that formed square arrays of about 4000 nm total size. While the frequency of precession of the magnetization of the 6000 nm element could be described with a macrospin model, the frequencies observed in the arrays of submicron size elements differed from the macrospin prediction. This observation may be understood in terms of the increasing nonuniformity of the demagnetizing field as the element aspect ratio is decreased