Electron spin dynamics of ferromagnetic Ga_1−x Mn_x As across the insulator-to-metal transition

Electron spin dephasing dynamics of ferromagnetic Ga_1−xMn_xAs with Mn concentration spanning from 0.5% to 15% across the insulator-to-metal transition is systematically studied using time-resolved magneto-optical Kerr effect measurements. In the insulating Ga_1−xMn_xAs, the impurity scattering and s-d exchange scattering induced by the magnetic impurity Mn ions are responsible for the electron spin dephasing process. While in the metallic and near metallic regime, the electron-electron Coulomb scattering becomes dominant over the impurity scattering on the spin dephasing process with D'yakonov-Perel' mechanism. Our findings are important for better engineering of Mn impurity doping in order to achieve potential Ga_1−xMn_xAs-based spintronics application.