  The theory of spin relaxation of conduction electrons is developed for
zinc-blende-type quantum wells grown on (110)-oriented substrate. It is shown
that, in asymmetric structures, the relaxation of electron spin initially
oriented along the growth direction is characterized by two different lifetimes
and leads to the appearance of an in-plane spin component. The magnitude and
sign of the in-plane component are determined by the structure inversion
asymmetry of the quantum well and can be tuned by the gate voltage. In an
external magnetic field, the interplay of cyclotron motion of carriers and the
Larmor precession of electron spin can result in a nonmonotonic dependence of
the spin density on the magnetic field.
