AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI-FrM

Paper MI-FrM6
Reversal Mechanism of Patterned Co/Pd Multilayer Islands

Friday, November 19, 2004, 10:00 am, Room 304A

Session: Advanced Magnetic Data Storage and Thin Film Processing
Presenter: B.D. Terris, Hitachi Global Storage Technologies
Authors: G. Hu, Hitachi Global Storage Technologies
T. Thomson, Hitachi Global Storage Technologies
C.T. Rettner, IBM Almaden Research Center
B.D. Terris, Hitachi Global Storage Technologies
Correspondent: Click to Email
Arrays of patterned Co/Pd magnetic islands with perpendicular anisotropy and sizes ranging from 30nm to 5 microns have been fabricated and characterized. Applying a field along the easy axis results in individual magnetic islands switching as a single unit, as observed by the magnetic optic Kerr effect and magnetic force microscope (MFM) measurements. The angle dependence of switching closely resembles the behavior predicted by the Stoner-Wohlfarth model with a minimum in island coercivity at 45 degrees. These results are expected for small islands which may reverse by rotation, but are surprising for the larger islands. The nominally identical continuous film exhibits a completely different behavior, where the film coercivity increases with the angle (t) between the applied field and film normal as 1/cos(t), as predicted for domain wall motion controlled reversal. These data leads to a model whereby the reversal of the larger islands is controlled by a nucleation event, followed by a rapid wall motion. The observed switching field of the island is the switching field of the small nucleation site, which reverses coherently. To test this model, we artificially introduce nucleation sites into the islands by applying an in-plane field. This results in a domain wall motion controlled angle dependent behavior in all islands capable of supporting a multi-domain ground state (size ranging from 200nm to 5 microns). The reversal behavior of the larger islands therefore depends on the initial state of the islands. In an island with no nucleation sites the reversal is governed by rotation, whereas in the same island into which nucleation sites have been pre-created, the reversal is governed by wall motion.