  The influence of the intrinsic spin of electrons on the propagation of
circularly polarized waves in a magnetized plasma is considered. New eigenmodes
are identified, one of which propagates below the electron cyclotron frequency,
one above the spin-precession frequency, and another close to the
spin-precession frequency.\ The latter corresponds to the spin modes in
ferromagnets under certain conditions. In the nonrelativistic motion of
electrons, the spin effects become noticeable even when the external magnetic
field $B_{0}$ is below the quantum critical\ magnetic field strength, i.e.,
$B_{0}<$ $B_{Q} =4.4138\times10^{9}\, \mathrm{T}$ and the electron density
satisfies $n_{0} \gg n_{c}\simeq10^{32}$m$^{-3}$. The importance of electron
spin (paramagnetic) resonance (ESR) for plasma diagnostics is discussed.
