  We compute damping of mechanical oscillations of a cantilever that contains
flipping paramagnetic spins. This kind of damping is mandated by the dynamics
of the total angular momentum, spin + mechanical. Rigorous expression for the
damping rate is derived in terms of measurable parameters. The effect of spins
on the quality factor of the cantilever can be significant in cantilevers of
small length that have large concentration of paramagnetic spins of atomic
and/or nuclear origin.
