The phenomenon of Anderson localization is studied for a class of one-particle
Schrödinger operators with random Zeeman interactions. These operators arise
as follows: Static spins are placed randomly on the sites of a simple cubic lattice
according to a site percolation process with density x and coupled to one another
ferromagnetically. Scattering of an electron in a conduction band at these spins is
described by a random Zeeman interaction term that originates from indirect exchange.
It is shown rigorously using a multiscale analysis that, for positive values of x
below the percolation threshold, the spectrum of the one-electron Schrödinger operator
near the band edges is dense pure-point, and the corresponding eigenfunctions
are exponentially localized.