Effect of stray field on local spin modes in exchange-biased magnetic tunnel junction elements

We report on the detection of localized spin modes in a multilayered spintronic device by means of time-resolved scanning Kerr microscopy. Measurements on this 13×9 µ m2 exchange-biased magnetic tunnel junction element at different applied bias fields indicate a strong effect of the stray field from the pinned CoFe layer on the magnetization dynamics in the free NiFe layer. This view is supported by micromagnetic simulations, which also show that the dynamics can be attributed to the specific shape of the internal magnetic field in the element. © 2005 American Institute of Physics