  Thin films of polycrystalline $\beta$-Mn structure CoZn have been grown on
thermally oxidized Si substrates by co-sputtering from elemental targets
followed by annealing. A range of films grown with variable Co deposition power
and fixed Zn deposition power were produced, so as to vary the proportions of
the two elements reaching the substrate, which were annealed post-growth.
Whilst all films exhibited a (211) $\beta$-Mn structure CoZn texture in X-ray
diffraction, transmission electron microscopy showed that the composition with
the highest integrated intensity for that Bragg peak contained large vacancies
and was covered by a thick ZnO cap owing to being Co-deficient overall. CoZn
films deposited at ratios tuned to give the optimal volume fraction of
$\beta$-Mn were continuous, with crystallites up to 200~nm in size, with a much
thinner ZnO cap layer. Magnetic measurements show that such optimal CoZn films
have a Curie temperature $T_\mathrm{C} \sim 420$~K and saturation magnetization
of 120~emu/cm$^3$, properties close to those reported for bulk crystals. The
$\beta$-Mn structure is chiral (P4$_{1}$32/P4$_{3}$32 space group) and is known
to give rise to a Dzyaloshinkii-Moriya interaction (DMI) that stabilizes
room-temperature skyrmions in the bulk. Our thin films are thus a potential
materials platform, compatible with planar processing technology, for magnetic
skyrmions arising from a bulk DMI.
