Ferromagnetic layer thickness dependence of the misalignment between anisotropy axes in Co/IrMn bilayers

In this work, exchange-biased Co/IrMn bilayers were fabricated by dc magnetron sputtering at room temperature. We investigated the misalignment angle between uniaxial and unidirectional anisotropies by measuring in-plane angular dependent ferromagnetic resonance. We found that the misalignment angle decreases with the ferromagnetic-layer (Co) thickness increasing. An asymmetric magnetization reversal phenomenon was also observed due to the misalignment anisotropy. By rotating the sample to a certain angle which respond to the direction of effective easy axis of uniaxial and unidirectional anisotropies, the asymmetry magnetization reversal can be effectively eliminated.