  In a recent study of the magnetic properties of rare-earth systems the two
extreme situations have been considered in which the crystalline electrostatic
field is large or small with respect to the spin-orbit interaction. In the
first case the orbitals of localized electrons are firmly coupled to the
lattice so that while an applied magnetic field rotates the spin, the charge
profile remains fixed to the lattice. In the second case an applied magnetic
field rotates both spin and density profile, even though through a very small
angle. We show that in this second case we have, in addition to the use of
photons or electrons, the possibility of exciting and observing the Scissors
Mode in crystals in a way analogous to that used in Bose-Einstein Condensates.
