  It has been well established that both in bulk at ambient pressure and for
films under modest strains, cubic SrCoO$_{3-\delta}$ ($\delta < 0.2$) is a
ferromagnetic metal. Recent theoretical work, however, indicates that a
magnetic phase transition to an antiferromagnetic structure could occur under
large strain accompanied by a metal-insulator transition. We have observed a
strain-induced ferromagnetic to antiferromagnetic phase transition in
SrCoO$_{3-\delta}$ films grown on DyScO$_3$ substrates, which provide a large
tensile epitaxial strain, as compared to ferromagnetic films under lower
tensile strain on SrTiO$_3$ substrates. Magnetometry results demonstrate the
existence of antiferromagnetic spin correlations and neutron diffraction
experiments provide a direct evidence for a G-type antiferromagnetic structure
with Ne\'el temperatures between $T_N \sim 135\,\pm\,10\,K$ and $\sim
325\,\pm\,10\,K$ depending on the oxygen content of the samples. Therefore, our
data experimentally confirm the predicted strain-induced magnetic phase
transition to an antiferromagnetic state for SrCoO$_{3-\delta}$ thin films
under large epitaxial strain.
