We fabricated an FePt/MgO tunneling junction (Fe<sub>55</sub>Pt<sub>45</sub>) with out-of-plane magnetization on a GaAs-based light-emitting-diode structure. The technique of spin-polarized electroluminescence (EL) was used to study the electrical spin
injection from FePt into GaAs at room temperature. Under the magnetic field of 1 T the spin polarization of the injected
electrons was at least 6.0%. The zero-magnetic-field spin polarization, which indicates the spin injection without
magnetic field, was at least 3.3%.
Time- and spatial-resolved circular-polarized photoluminescence measurement was performed on an <i>n</i>-type modulation-doped (Cd,Mn)Te quantum well. The spatial extent of PL in the right circular polarization (RCP) got broad with an increase in magnetic field, although, for the left circular polarization (LCP), the extent showed a tendency to contract with the magnetic field. This difference between RCP and LCP is considered to be resulting from the difficulty difference in the formation of a negatively-charged exciton X<sup>-</sup>. We successfully observed the time-development of an electric-field-induced drift of X<sup>-</sup>. The drift of X<sup>-</sup> was found to be promoted by the magnetic fields. This is considered to originate in the suppression of an exciton-magnetic-polaron formation or/and the decrease of a <i>simple</i> spin scattering under the magnetic fields. The scattering time of X<sup>-</sup> was found to be about the same value as that of the two-dimensional conduction electron. This is the same result as the case of an <i>n</i>-type modulation-doped GaAs quantum well which had been already reported by other group (See References 4 and 5).