  We present Monte Carlo simulations of hysteresis loops of a model of a
magnetic nanoparticle with a ferromagnetic core and an antiferromegnetic shell
with varying values of the core/shell interface exchange coupling which aim to
clarify the microscopic origin of exchange bias observed experimentally. We
have found loops shifts in the field direction as well as displacements along
the magnetization axis that increase in magnitude when increasing the
interfacial exchange coupling. Ovelap functions computed from the spin
configurations along the loops have been computed to explain the origin and
magnitude of these features microscopically.
