  We report the growth, structural and magnetic properties of the less studied
Eu-oxide phase, Eu$_3$O$_4$, thin films grown on a Si/SiO$_2$ substrate and
Si/SiO$_2$/graphene using molecular beam epitaxy. The X-ray diffraction scans
show that highly-textured crystalline Eu$_3$O$_4$(001) films are grown on both
substrates, whereas the film deposited on graphene has a better crystallinity
than that grown on the Si/SiO$_2$ substrate. The SQUID measurements show that
both films have a Curie temperature of about 5.5 K, with a magnetic moment of
0.0032 emu/g at 2 K. The mixed-valency of the Eu cations has been confirmed by
the qualitative analysis of the depth-profile X-ray photoelectron spectroscopy
measurements with the Eu$^{2+}$ : Eu$^{3+}$ ratio of 28 : 72. However,
surprisingly, our films show no metamagnetic behaviour as reported for the bulk
and powder form. Furthermore, the Raman spectroscopy scans show that the growth
of the Eu$_3$O$_4$ thin films has no damaging effect on the underlayer graphene
sheet. Therefore, the graphene layer is expected to retain its properties.
