  We give a necessary and sufficient condition, of geometric type, for the
uniform decay of energy of solutions of the linear system of magnetoelasticity
in a bounded domain with smooth boundary. A Dirichlet-type boundary condition
is assumed. When the geometrical condition is not fulfilled, we show polynomial
decay of the energy, for smooth initial conditions. Our strategy is to use
micro-local defect measures to show suitable observability inequalities on
high-frequency solutions of the Lame system.
