  We coherently manipulate spin correlations in a two-component atomic Fermi
gas loaded into an optical lattice using spatially and time-resolved Ramsey
spectroscopy combined with high-resolution \textit{in situ} imaging. This novel
technique allows us not only to imprint spin patterns but also to probe the
static magnetic structure factor at arbitrary wave vector, in particular the
staggered structure factor. From a measurement along the diagonal of the
$1^\mathrm{st}$ Brillouin zone of the optical lattice, we determine the
magnetic correlation length and the individual spatial spin correlators. At
half filling, the staggered magnetic structure factor serves as a sensitive
thermometer for the spin temperature, which we employ to study the
thermalization of spin and density degrees of freedom during a slow quench of
the lattice depth.
