M. Wilkinson et al., MAGNETIC DIPOLE ABSORPTION OF RADIATION IN SMALL CONDUCTING PARTICLES, Journal of physics. Condensed matter, 10(12), 1998, pp. 2739-2758
We give a theoretical treatment of magnetic dipole absorption of elect
romagnetic radiation in small conducting particles, at photon energies
which are large compared to the single-particle level spacing, and sm
all compared to the plasma frequency. We discuss both diffusive and ba
llistic electron dynamics for particles of arbitrary shape. The conduc
tivity becomes non-local when the frequency is smaller than the freque
ncy omega(c) characterizing the transit of electrons from one side of
the particle to the other, but in the diffusive case omega(c) plays no
role in determining the absorption coefficient. In the ballistic case
, the absorption coefficient is proportional to omega(2) for omega <<
omega(c), but is a decreasing function of w for omega >> omega(c).