Time stability of multi-domain states formed in the magnetization reversal process of GaMnAs film

The magnetization reversal process of ferromagnetic GaMnAs epilayers has been systematically investigated using the planar Hall effect (PHE) and magnetoresistance (MR). We have observed non-abrupt transitions between two orientations of magnetization in PHE and striking resistance dips at the second switching in MR. The observed behaviors indicate that multi-domain structures are formed as magnetization undergoes a reorientation. An asymmetric PHE hysteresis loop was obtained when the range of the field scan was restricted to fields below the final magnetization transition. This indicates that the domain structure formed at the moment of magnetization reorientation remains stable even after the magnetic field is removed. The time stability of the multi-domain structure was further tested by monitoring the change in the planar Hall resistance value for more than 24 h.