SPIN-FLIP SCATTERING NEAR THE METAL-TO-INSULATOR TRANSITION IN CD0.95MN0.05SE-IN

Spin dynamics of electrons in n-type Cd0.95Mn0.05Se near the metal-to-insulator transition are probed by means of inelastic-light-scattering measurements as a function of magnetic field up to 8 T and temperature down to 0.25 K. The observed Raman spin-flip scattering line is demonstrated to arise from itinerant (diffusive) electrons. The spin-split energies (Stokes shifts), being determined by the s-d exchange interaction, increase strongly as the temperature is lowered, and at 0.25 K attain values that correspond to an effective Lande factor as large as 500. Variations of the spin-split energy with the magnetic field follow a modified Brillouin function suitable for this diluted magnetic semiconductor in a paramagnetic phase. A better description of experimental results is obtained, however, assuming the existence of an additional magnetization that depends only weakly on the external magnetic field. Such magnetization could be induced by bound magnetic polarons, and, therefore, its appearance points indirectly to the presence of local s spins on the metallic side of the metal-to-insulator transition. Studies of the linewidth in forward- and backscattering geometries provide information on the spin-relaxation time T2 and spin-diffusion coefficient D(s) of itinerant electrons. The magnitude of T2 is shown to be primarily determined by (i) spin-flip scattering of electrons by magnetic ions and (ii) motionally narrowed inhomogeneous broadening caused by compositional fluctuations of magnetization. It is demonstrated that, in agreement with theoretical expectations, both T2 and D(s) are strongly affected by electron-electron interactions and localization corrections.