  The ground states and collective excitations of trapped Fermion gases
consisting of atoms with magnetic dipole moment are studied using a
time-dependent density-matrix approach. The advantages of the density-matrix
approach are that one-body and two-body observables are directly calculated
using one-body and two-body density matrices and that it has a clear relation
to the Hartree-Fock (HF) and time-dependent HF theory. The HF calculations show
the magnetization of the gases when the dipole-dipole interaction is strong. It
is shown that the tensor properties of the dipole-dipole interaction are
revealed in the excitation modes associated with spin degrees of freedom.
