Spin relaxation of 2D electron in Si/SiGe quantum well suppressed by applied magnetic field

We investigate spin resonance of two-dimensional (213) conduction electrons in a modulation-doped SiGe/Si/SiGe quantum well structure. We find spin relaxation times of the order of microseconds and a 2D anisotropy of both the line broadening (dephasing time) and of the longitudinal spin relaxation. The spin relaxation is dominated by the D'yakonov-Perel spin relaxation mechanism originating from the Bychkov-Rashba spin-orbit field. We find evidence that for high mobility samples the cyclotron motion causes an additional modulation of spin-orbit coupling which leads to an effective reduction of the spin relaxation. For 2D electrons the dependence of the cyclotron frequency on the direction of applied field causes the observed anisotropy of spin relaxation.