Magnetic dispersion in exchange coupled PdPtMn/CoFe bilayers

The effect of rotating magnetic field annealing on the microscopic and macroscopic magnetic properties of exchange coupled antiferromagnetic/ferromagnetic PdPtMn/CoFe bilayers was studied using magnetic force microscopy and vibrating sample magnetometry. It was found that the local fluctuations in the magnetization direction increased with increasing rotating field annealing temperature, which was accompanied by a decrease in the observable exchange anisotropy field without a change in the angular dependence. The results are consistent with the thermal fluctuation model allowing random orientation of the exchange coupling for coupling regions with blocking temperatures smaller than the annealing temperature