An array of micron-sized square Permalloy (TM) elements exhibits pure nucleation behavior under selected ranges of applied field and temperature. As a consequence, macroscopically observed net magnetization loss with logarithm of time can be correlated with discrete vortex nucleation events using in situ Lorentz microscopy. Application of various magnetic fields revealed different resistances to nucleation. Using the Arrhenius-Neel model, the energy barrier to magnetic vortex nucleation is measured and a clear dependence on the applied field is observed. (c) 2006 American Institute of Physics.
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