Probing activation energy barrier distribution for reversal of strongly exchange-coupled magnetic multilayer thin films

We demonstrate a measurement technique with zero-applied magnetic field to deduce and spatially map the activation energy barrier distribution of strongly exchange-coupled magnetic-multilayer thin films, which is otherwise inaccessible with conventional methods in the presence of an applied magnetic field. Our technique involves the analysis of magnetic force microscopy images of magnetic microwires, whose magnetizations have been subject to thermal decay due to Joule heating from applied nanosecond scale current pulses. Fitting the results of such measurements on CoNi/Pd magnetic-multilayer microwires to a modified Arrhenius-Neel formalism yields an energy barrier distribution with 8% sigma, in good agreement with complementary fits of the switching-field-distribution measurements on patterned CoNi/Pd magnetic-multilayer islands.