  We exploit ferromagnetic imprinting to create complex laterally defined
regions of nuclear spin polarization in lithographically patterned MnAs/GaAs
epilayers grown by molecular beam epitaxy (MBE). A time-resolved Kerr rotation
microscope with approximately 1 micron spatial resolution uses electron spin
precession to directly image the GaAs nuclear polarization. These measurements
indicate that the polarization varies from a maximum under magnetic mesas to
zero several microns from the mesa perimeter, resulting in large (10**4 T/m)
effective field gradients. The results reveal a flexible scheme for lateral
engineering of spin-dependent energy landscapes in the solid state.
