In our recent studies the relaxation processes were investigated by ferromagnetic resonance (FMR) using magnetic single, Au/Fe/GaAS(0 0 1),
and double layer, Au/Fe/Au/Fe/GaAS(0 0 1), structures prepared by
molecular beam epitaxy (MBE). Single and double layer structures were
grown on (4 x 6) reconstructed GaAS(00 1) templates. The samples have
high crystalline quality with the magnetic properties corresponding to
bulk Fe, only modified by interface anisotropies. The magnetic
relaxation in these structures is well described by Gilbert damping
with no extrinsic contributions to the FMR line width. These structures
provide an excellent opportunity to investigate non-local damping which
is caused by spin transport across a non-magnetic spacer. In the double
layer structures thin Fe layers were separated from a second thick Fe
layer of 40 monolayer (M L) thickness by a 40 ML thick Au(001) spacer.
The main result of these studies is that the ultrathin Fe films in
magnetic double layers acquire an additional Gilbert damping. The
additional FMR line width followed an inverse dependence on the Fe film
thickness which is expected for interface damping. The spin pump model
will be discussed and it will be shown that it is closely related to
the dynamic part of interlayer exchange coupling. (C) 2002 Elsevier
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