  The first order quantum correction to the power of spontaneous radiation of
electrons in an arbitrary two-component periodic magnetic field was obtained.
The phenomenon of selfpolarization of the spin of electrons in a process of
spontaneous radiation was also studied. By electron's motion in a spiral
magnetic undulator, the quantitative characteristics of selfpolarization (the
polarization degree and the relaxation time) are different from corresponding
ones in synchrotron radiation. The limiting cases of near-axis and
ultrarelativistic approximation were considered.
