Asymmetric Magnetization Reversal in IrMn/CoFe/FeO$_rm X$/CoFe Structures

We analyzed anisotropy in IrMn/CoFe/FeO$_ X$/CoFe multilayers with angular remanence measurements. The results showed the coexistence of biquadratic and unidirectional anisotropies. A significantly asymmetric magnetization reversal had been observed. We studied the reversal mechanism by using vector coils and suggested that the switching in the decreasing branch comprised both coherent rotation and 90$^circ$domain wall motion; however, the switching in the increasing branch showed complicated multidomain rotation.