  Progress in spintronics has been aided by characterization tools tailored to
certain archetypical materials. New device structures and materials will
require characterization tools that are material independent, provide
sufficient resolution to image locally-varying spin properties and enable
subsurface imaging. Here we report the demonstration of a novel spin-microscopy
tool based on the variation of a global spin-precession signal in response to
the localized magnetic field of a scanned probe. We map the local spin density
in optically pumped GaAs from this spatially-averaged signal with a resolution
of 5.5 microns. This methodology is also applicable to other spin properties
and its resolution can be improved. It can extend spin microscopy to device
structures not accessible by other techniques, such as buried interfaces and
non-optically active materials, due to the universal nature of magnetic
interactions between the spins and the probe.
