  Recently, focused electron beam induced deposition has been employed to
prepare functional magnetic nanostructures with potential in nanomagnetic logic
and sensing applications by using homonuclear precursor gases like Fe(CO)5 or
Co2(CO)8. Here we show that an extension towards the fabrication of bi-metallic
compounds is possible by using a single-source heteronuclear precursor gas. We
have grown CoFe alloy magnetic nanostructures from the HFeCo3(CO)12 metal
carbonyl precursor. The compositional analysis indicate that the samples
contain about 80 at% of metal and 10 at% of carbon and oxygen. Four-probe
magnetotransport measurements are carried out on nanowires of various sizes
down to a width of 50 nm, for which the room temperature resistivity of
43~$\mu\Omega$cm is found. Micro-Hall magnetometry reveals that
50~nm$\times$250~nm nanobars of the material are ferromagnetic up to the
highest measured temperature of 250 K. Finally, the TEM microstructural
investigation shows that the deposits consist of a bcc Co-Fe phase mixed with a
FeCo2O4 spinel oxide phase with nanograins of about 5 nm diameter.
