Experimental study of the microscopic mechanisms of magnetization reversal inFeNi∕FeMnexchange-biased ferromagnet/antiferromagnet polycrystalline bilayers using the magneto-optical indicator film technique

Abstract

Remagnetization of the $\mathrm{FeNi}∕\mathrm{FeMn}$ bilayer was investigated using the magneto-optical indicator film imaging technique. We show the formation and breakdown of the homogeneous exchange spring into exchange springs of opposite chiralities during reversal in a rotating magnetic field. In reversal with a linear field, contrary to theoretical predictions, the winding of the exchange spring occurs without net magnetization rotation. It initiates by the formation of local spin spirals with opposite chirality and terminates with the formation of a single chiral state through the propagation of a specific kind of boundary separating regions with this single chirality from those with the mixed chiral state.