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Characterization of domain states in submicron sized permalloy
particles with perpendicular anisotropy
Peter Eames and E. Dan Dahlberg
Magnetic force microscopy (MFM) with in situ magnetic fields was used to
classify and determine the distributions of magnetic domain structures in
190-nm-thick Ni81Fe19 particles with diameters from 850 to 250 nm. A
deposition induced perpendicular anisotropy energy resulted in a simple
stripe domain pattern observed in MFM images on unpatterned witness films.
The domain structures in the particles are not stripes but consist of a
small number of distinct magnetization states for each diameter of
particle. Repeated in-plane magnetic field saturations were applied to
effectively anneal the magnetic states of an array of same diameter
particles. For some of the states Boltzmann statistics were used to
calculate an "energy ratio" of the particles magnetization states based on
the observed distribution for each diameter.