Ultrafast dynamics of four-state magnetization reversal in (Ga,Mn)As

The ultrafast dynamics of in-plane four-state magnetization reversal from compressively strained (Ga,Mn)As film was investigated by magneto-optical Kerr rotation measurement. The magnetization reversal signal was dramatically suppressed upon pumping, and recovered slowly with time evolution. The low switching field H-c1 increased abruptly from 30 to 108 G on the first several picoseconds and recovered back to the value before optical pumping within about 500 ps, whereas the high switching field H-c2 did not change obviously upon pumping, implying a domain-wall nucleation/propagation at low fields and coherent magnetization rotation at high fields in the magnetization reversal process.

National Natural Science Foundation of China 10674131 60836002National Key Projects for Basic Research of China 2007CB924904 Knowledge Innovation Project of Chinese Academy of Sciences KJCX2. YW.W09 This work is supported by the National Natural Science Foundation of China (Grant Nos. 10674131 and 60836002) the National Key Projects for Basic Research of China under Grant No. 2007CB924904 and the Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KJCX2. YW.W09)