  We present a theory of the low-energy excitations of a ferromagnetic metal
nanoparticle. In addition to the particle-hole excitations, which occur in a
paramagnetic metal nanoparticle, we predict a branch of excitations involving
the magnetization-orientation collective coordinate. Tunneling matrix elements
are in general sizable for several different collective states associated with
the same band configuration. We point out that the average change in ground
state spin per added electron differs from non-interacting quasiparticle
expectations, and that the change in the spin-polarization, due to Zeeman
coupling, is strongly influenced by Coulomb blockade physics.
