Spin relaxation and dephasing mechanism in (Ga,Mn)As studied by time-resolved Kerr rotation

Spin dynamics in (Ga,Mn)As films grown on GaAs(001) was investigated by Time-resolved magneto-optical Kerr effect. The Kerr signal decay time of (Ga,Mn)As without external magnetic field applied was found to be several hundreds picoseconds, which suggested that photogenerated polarized holes and magnetic ions are coupled as a ferromagnetic system. Nonmonotonic temperature dependence of relaxation and dephasing (R&D) time and Larmor frequency manifests that Bir-Aronov-Pikus mechanism dominates the spin R&D time at low temperature, while D'yakonov-Perel mechanism dominates the spin R&D time at high temperature, and the crossover between the two regimes is Curie temperature.

National Natural Science Foundation of China 1067 4130 60836002National Key Projects for Basic Research of China 2007CB924904 Chinese Academy of Sciences KJCX2. YW. W09 The authors are grateful to Professor Baoquan Sun for technical assistance and fruitful discussion. This work is supported by the National Natural Science Foundation of China (rant Nos. 1067 4130 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 (rant No. KJCX2. YW. W09).