  Effect of magnetic field on electron spin relaxation in quantum wells is
studied theoretically. We have shown that Larmor effect and cyclotron motion of
carriers can either jointly suppress D'yakonov-Perel' spin relaxation or
compensate each other. The spin relaxation rates tensor is derived for any
given direction of the external field and arbitrary ratio of bulk and
structural contributions to spin splitting. Our results are applied to the
experiments on electron spin resonance in SiGe heterostructures, and enable us
to extract spin splitting value for such quantum wells.
