The exchange bias (EB) phenomenon is associated with an exchange coupling between ferromagnetic (F) and antiferromagnetic (AF) layers across their common interface, resulting in a unidirectional magnetic anisotropy and a shift of the magnetic hysteresis by an exchange bias field HB, after field cooling the F/AF bilayer below the blocking temperature T_B < T_N of the AF layer.

The upper panel shows a magnetic hysteresis, measured by the magneto-optic Kerr effect after field cooling in an external field below the T_N.

The lower panels reproduce the spin-flip (SF) and non-spin-flip (NSF) intensities for the descending (left) and ascending (right) part of the hysteresis loop. Note the different SF intensities at both coercive fields (indicated by the arrows), being characteristic for domain wall motion (left) and coherent rotation (right)

(Courtesy of F. Radu)