  We have observed conventional signature of exchange bias (EB), in form of
shift in field-cooled (FC) hysteresis loop, and training effect, in
BiFe0.8Mn0.2O3 nanoparticles. From neutron diffraction, thermoremanent
magnetization and isothermoremanent magnetization measurements, the
nanoparticles are found to be core-shell in nature, consisting of an
antiferromagnetic (AFM) core, and a 2-dimensional diluted AFM (DAFF) shell with
a net magnetization under a field. The analysis of the training effect data
using the Binek's model shows that the observed loop shift arises entirely due
to an interface exchange coupling between core and shell, and the intrinsic
contribution of the DAFF shell to the total loop shift is zero. A significantly
high value of EB field has been observed at room temperature. The present study
is useful to understand the origin of EB in other DAFF-based systems as well.
