  We calculate the magnetization hysteresis for an ordered array of composite
magnetic nanoparticles with a ferromagnetic (FM) core and an antiferromagnetic
(AFM) shell, located on a triangular lattice and coupled via magnetostatic
forces. Each nanoparticle is described by a pair of exchange-coupled (J),
anisotropic spins (Meiklejohn-Bean model). The magnetization hysteresis loop is
obtained using the Metropolis Monte Carlo algorithm. For magnetically hard
nanoparticles we find that the coercivity is reduced with increasing the
dipolar coupling strength, while the exchange bias field shows an
non-monotonous behavior resulting from the competition between the random
anisotropy and interparticle dipolar interactions. The possibility of enhancing
the exchange bias field by increasing the packing density is discussed.
