  We studied exchange bias in magnetic multilayers incorporating
antiferromagent CoO doped with up to 35 atomic percent of Pt. The exchange bias
increased with doping in epitaxial films, but did not significantly change in
polycrystalline films at the lowest measured temperature of 5 K, and decreased
at higher temperatures. We explain our results by the increased granularity of
the doped antiferromagnetic films, resulting in simultaneous enhancement of the
uncompensated spin density and reduction of the magnetic stability of
antiferromagnetic grains.
