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A theory for longitudinal (T 1 ) and transverse (T 2 ) electron spin coherence times in zincblende semiconductor quantum wells is developed based on a non-perturbative nanostructure model solved in a fourteen-band restricted basis set. Distinctly different dependences of coherence times on mobility, quantization energy, and temperature are found from previous calculations. Quantitative agreement between our calculations and measurements is foundfor GaAs/AlGaAs, InGaAs/InP, and GaSb/AlSb quantum wells.

Time-resolved optical measurements in (110)-oriented GaAs/AlGaAs quantum wells show a tenfold increase of the spin-relaxation rate as a function of applied electric field from 20 to 80 kV cm(-1) at 170 K and indicate a similar variation at 300 K, in agreement with calculations based on the Rashba effect. Spin relaxation is almost field independent below 20 kV cm(-1) reflecting quantum well interface asymmetry. The results indicate the achievability of a voltage-gateable spin-memory time longer than 3 ns simultaneously with a high electron mobility.

Time-resolved optical techniques are used to explore electron spin dynamics in bulk and epilayer samples of n-type ZnO as a function of temperature and magnetic field. The bulk sample yields a spin coherence time T * 2 of 20 ns at T = 30 K. Epilayer samples, grown by pulsed laser deposition, show a maximum T * 2 of 2 ns at T = 10 K, with spin precession persisting up to T = 280 K.A lot of attention has been focused on zinc oxide (ZnO) because of material properties that make it well-suited for applications in ultra-violet light emitters, transparent high-power electronics and piezoelectric transducers. In addition, the theoretical work of Dietl et al ., 1 predicting room temperature ferromagnetism for Mn-doped p-type ZnO, has revealed the possibility that ZnO may be an appropriate candidate for spintronics. 2 The magnetic properties of thin films of ZnO with transition ion doping, 3,4,5 are being widely investigated, but practical spintronics applications would also require long spin coherence time and spin coherence length.

We investigate electrically induced spin currents generated by the spin Hall effect in GaAs structures that distinguish edge effects from spin transport. Using Kerr rotation microscopy to image the spin polarization, we demonstrate that the observed spin accumulation is due to a transverse bulk electron spin current, which can drive spin polarization nearly 40 microns into a region in which there is minimal electric field. Using a model that incorporates the effects of spin drift, we determine the transverse spin drift velocity from the magnetic field dependence of the spin polarization.