  Recently synthesized metastable tetragonal CoSe, isostructural to the FeSe
superconductor, offers a new avenue for investigating systems in close
proximity to the iron-based superconductors. We present magnetic and transport
property measurements on powders and single crystals of CoSe. High field
magnetic susceptibility measurements indicate a suppression of the previously
reported 10 K ferromagnetic transition with the magnetic susceptibility
exhibiting time-dependence below the proposed transition. Dynamic scaling
analysis of the time-dependence yields a critical relaxation time of $\tau^{*}
= 0.064 \pm 0.008 $ s which in turn yields an activation energy of $E_{a}^{*}$
= 14.84 $\pm$ 0.59 K and an ideal glass temperature $T_{0}^{*}$ = 8.91 $\pm$
0.09 K from Vogel-Fulcher analysis. No transition is observed in resistivity
and specific heat measurements, but both measurements indicate that CoSe is
metallic. These results are interpreted on the basis of CoSe exhibiting
frustrated magnetic ordering arising from competing magnetic interactions.
Arrott analysis of single crystal magnetic susceptibility has indicated that
the magnetic moments lie in the $ab$-plane so frustration may arise from
intralayer magnetic fluctuations as well as interlayer coupling. The results
have implications for understanding the superconductivity in the iron
chalcogenide systems as well as utilizing CoSe as a host for chemical and
physical manipulation to tune and explore emergent phenomena within an
expanding new class of transition metal chalcogenides.
