Magnetoresistance measurements have been performed on a set
of MBE-grown Fe-Cr-Fe sandwiches with different chromium
thicknesses, 12Å < tCr < 28 Å.
For 13 Å < tCr < 24 Å,
magnetization measurements show that the Fe moments are
antialigned at zero field. For samples exhibiting zero-field
antialignment, negative magnetoresistance steps are observed
at applied fields where discontinuities occur in the
magnetization curve. The size of the magnetoresistance steps
increases with increasing antiferromagnetic coupling between
the Fe layers. The magnetoresistance (r(H) - r(0))/r(0) is
approximately proportional to cos2(DeltaPhi/2),
where DeltaPhi = (Phi1 - Phi2), and Phi1(H) and Phi2(H) are
the angles that the individual moments of the two Fe films
make with the in-plane easy <100> axis.