Asymmetric motion of an exchange-biased magnetic domain wall in magnetic wires

The magnetization reversal dynamics of a magnetic domain wall (DW) in epitaxial CoO/Co magnetic wires with perpendicular anisotropy is studied between 10-300 K using extraordinary Hall effect measurements. In particular, the average DW velocity of the DW exchange coupled to the antiferromagnetic (AF) CoO layer is measured and analyzed. It is found that above the blocking temperature T_B, the DW propagates easily and symmetrically on both sides of the hysteresis loop, however, below T_B the DW motion becomes asymmetric where the hysteresis loop of the wire exhibit an exchange bias field as high as 1500 Oe at 30 K. These results indicate that AF coupling provides an extra source of pinning that increases the domain wall thermal stability, and that such pinning of the DW can be strongly increased by using an exchange bias field.