Effect of Interface Structure on Exchange Biased Heusler Alloy Films

We report on the effects of grain size in antiferromagnetic IrMn layers exchange bias to
${\rm Co}_{2}{\rm FeSi}$
. We also report on an enhanced effect where Mn layers are inserted in the interface. The exchange-biased IrMn/
${\rm Co}_{2}{\rm FeSi}$
samples were grown by a HiTUS system, which allows us to control the grain size. The smaller IrMn grains were too small to give a large
$H_{ex}$
while an Mn layer 0.5 nm thick dramatically increased
$H_{ex}$
. This significant increase is attributed to optimization of the Mn concentration at the interface. This grain-size and interface tuning offers a way to control the exchange bias in such systems.