  We report the crystal growth, crystal structure and basic magnetic properties
of a new cobalt-based pyrochlore, NaSrCo$_2$F$_7$. Na and Sr are completely
disordered on the non-magnetic large atom A sites, while magnetic S=3/2
Co$^{2+}$ fully occupies the pyrochlore lattice B sites. This system exhibits
an isotropic magnetic susceptibility with strong antiferromagnetic interactions
(${\theta}_{CW}$ = -127(1)), a large effective moment (${\rho_{eff}}$ = 5.9(1)
${\mu_B}$/Co) and no spin freezing until 3 K. Thus NaSrCo$_2$F$_7$ is a
geometrically frustrated antiferromagnet with a frustration index f =
-${\theta_{CW}}$/T$_f$ = 42. AC susceptibility, DC susceptibility, and heat
capacity are utilized to characterize the spin freezing at low temperatures. We
propose that NaSrCo$_2$F$_7$, compared here to the related material
NaCaCo$_2$F$_7$, may be the realization of a frustrated pyrochlore
antiferromagnet with weak bond disorder. The strong magnetic frustration at an
easily accessible temperature and the availability of large single crystals
make this one of the potentially interesting alternatives to the more commonly
studied rare earth oxide pyrochlores.
