  We have studied the growth of metastable face-centered-cubic, non-magnetic
Fe78Ni22 thin films on silicon substrates. These films undergo a magnetic
(paramagnetic to ferromagnetic) and structural (fcc to bcc) phase
transformation upon ion beam irradiation and thus can serve as a template for
direct writing of magnetic nanostructures by the focused ion beam. So far,
these films were prepared only on single crystal Cu(100) substrates. We show
that transformable Fe78Ni22 thin films can also be prepared on a
hydrogen-terminated Si(100) with a 130-nm-thick Cu(100) buffer layer. The
H-Si(100) substrates can be prepared by hydrofluoric acid etching or by
annealing at 1200{\deg}C followed by adsorption of atomic hydrogen. The Cu(100)
buffer layer and Fe78Ni22 fcc metastable thin film were deposited by thermal
evaporation in an ultra-high vacuum. The films were consequently transformed
in-situ by 4keV Ar+ ion irradiation and ex-situ by a 30 keV Ga+ focused ion
beam, and their magnetic properties were studied by magneto-optical Kerr effect
magnetometry. The substitution of expensive copper single crystal substrate by
standard silicon wafers dramatically expands application possibilities of
metastable paramagnetic thin films for focused ion beam direct magnetic
patterning.
