The magnetostatic interactions and the disorder in an array of cylindrical Ni particles have been quantified. Room-temperature magnetic force microscopy data were used to determine the dipolar energy/particle for first, second, etc., nearest neighbor particles with external magnetic fields applied along the cylinder axes. An Ising-type model, which includes a distribution of anisotropy energies, accurately replicates the experimental dipolar energy/particle data and the observed hysteresis loops. The technique provides a method to quantify the magnetic properties of a magnetic particle system.
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The authors would like to acknowledge Dr. C. Campbell, Dr. P. Crowell, and Dr. M. Yan for helpful discussions. They also acknowledge the financial support provided by the ONR, the MRSEC Program of the National Science Foundation under Award No. DMR-0212302, and the NSF.