We report a new type of powder neutron diffraction experiment to obtain magnetic diffraction intensities by subtraction of patterns at varying applied magnetic fields. This method gives the size, direction, and location of spin moments in the ground state of the relatively complex 12 manganese cluster compound illustrated The ground state is Ising-like with opposed Mn(III) and Mn(IV) spin directions. The bridging oxo and carboxylate ligands carry significant spin density.