  The possibility of a solid state electron electric dipole moment (EDM)
experiment based on Gadolinium Iron Garnet (GdIG) is investigated. GdIG appears
to exhibit superparamagnetism and this effect can be used to enhance the
electric-field-induced EDM signal at relatively a high temperatures, as
compared to a simple paramagnetic system such as Gadolinium Gallium Garnet. The
sensitivity of a GdIG based experiment might be large enough that an
improvement by over three orders of magnitude, compared to the existing
electron EDM limit, could be obtained at a modest temperature of 4 K, assuming
that the superparamagnetic effect is not suppressed at this temperature, and
that the spin relaxation time remains sufficiently rapid.
