TIME-RESOLVED FARADAY-ROTATION SPECTROSCOPY OF SPIN DYNAMICS IN DIGITAL MAGNETIC HETEROSTRUCTURES

A time-resolved resonant Faraday rotation spectroscopy is employed to study the dynamical interplay between local magnetic moments and photo excited carrier spins in quantum-confined semiconductor geometries, Th is highly sensitive technique functions as an energy selective, noninv asive, all-optical probe of spin dynamics ranging from femtosecond to microsecond timescales and is particularly suited to low-dimensional s ystems having small numbers of magnetic spins. Carrier spin-scattering rates, lifetimes, and the orientation and relaxation of perturbed mag netic ions are directly observed in the time domain, The utility of th is technique is demonstrated through the study of a newly developed cl ass of magnetic heterostructure, in which fractional monolayer planes of magnetic Mn2+ ions are incorporated ''digitally'' into nonmagnetic II-VI ZnSe-ZnCdSe quantum wells. These digital magnetic heterostructur es (DMH) possess large g-factors and exhibit enormous low-field resona nt Faraday rotations in excess of 1.7 x 10(7) deg/T.cm at low temperat ures. Time-resolved Faraday rotation measurements identify a wealth of unexpected electronic and magnetic spin dynamics that are different f rom those generated in traditional semiconductors or alloyed diluted m agnetic semiconductor structures.