  We combine the Ramsey interferometry protocol, the Stern-Gerlach detection
scheme, and the use of elongated geometry of a cloud of fully polarized cold
cesium atoms to measure the selected component of the magnetic field gradient
along the atomic cloud in a single shot. In contrast to the standard method
where the precession of two spatially separated atomic clouds is simultaneously
measured to extract their phase difference, which is proportional to the
magnetic field gradient, we here demonstrate a gradiometer using a single image
of an expanding atomic cloud with the phase difference imprinted along the
cloud. Using resonant radio-frequency pulses and Stern-Gerlach imaging, we
first demonstrate nutation and Larmor precession of atomic magnetization in an
applied magnetic field. Next, we let the cold atom cloud expand in one
dimension and apply the protocol for measuring the magnetic field gradient. The
resolution of our single-shot gradiometer is not limited by thermal motion of
atoms and has an estimated absolute accuracy below $\pm0.2$~mG/cm
($\pm20$~nT/cm).
