  Structure of amorphous nangranular composite
(Co$_{86}$Nb$_{12}$Ta$_2$)$_x$(SiO$_2$)$_{1-x}$ films was studied by means of
grazing-incidence small-angle X-ray scattering as a function of atomic
concentration $x$ of the metal fraction in vicinity of the percolation
threshold. It has been established that the average size of magnetic
nanoparticles increases with $x$ and this increment exhibit the anisotropic
character. It was found that in a whole concentration range the particles are
elongated along the growth direction perpendicular to the film plane. For the
lowest concentration $x=0.193$ clusters with isotropic shape and average radius
of 1 nm were observed, while for higher concentrations up to $x=0.665$ the
average cluster length along the film normal is $1.5-7$ nm and the
cross-section is $1-2$ nm.
