  We calculate the plasmon frequency and damping rate of plasma oscillations in
a spin-polarized BLG system. Using the long wavelength approximation for
dynamical dielectric function, we obtain an analytical expression for plasmon
frequency showing that the degree of spin polarization P has negligible effect
on the long wavelength plasmon frequency. Numerical calculations demonstrate
that the degree of spin polarization affects slightly (strongly) plasmon
frequency at small (large) wave-vectors and the maximum value of damping rate
increases with increasing P. We also study the effects of carrier density and
substrate dielectric constant on plasmon properties for different value of spin
polarization. The numerically calculated critical wave-vector, at which the
plasmon dispersion curve hits the edge of electron-hole continuum, decreases
with P and can be used to determine experimentally the degree of spin
polarization.
