Ip. Smorchkova et al., SPIN TRANSPORT AND OPTICALLY-PROBED COHERENCE IN MAGNETIC SEMICONDUCTOR HETEROSTRUCTURES, Physica. B, Condensed matter, 251, 1998, pp. 676-684
Molecular beam epitaxy is used to ''spin engineer'' an environment whe
rein quantum-confined electronic states in a wide band gap II-VI semic
onductor quantum well (Zn1-xCdx Se) are strongly exchange-coupled to s
ystematic 2D distributions of localized spins (Mn2+ ions). Magneto-opt
ical spectroscopy of undoped structures demonstrates that such a schem
e successfully produces well-confined excitonic states whose Zeeman sp
litting in modest magnetic fields greatly exceeds the inhomogeneous li
ne widths. In modulation-doped structures, a combination of magneto-tr
ansport and magneto-optical measurements shows the formation of a ''ma
gnetic'' two-dimensional electron gas characterized by spin gaps which
are much larger than Landau level gaps. This results in a novel quant
um Hall system which can be highly spin polarized even at large fillin
g factors. Time-resolved Faraday/Kerr effect measurements in the Voigt
geometry probe the electronic spin dynamics of the exciton/electron g
as, revealing terahertz and gigahertz oscillations that originate from
the coherent spin precession of electrons and local moments, respecti
vely. (C) 1998 Elsevier Science B.V. All rights reserved.