Exchange bias in two-dimensional layers of interacting nanoparticles with random magnetic anisotropy: A Monte Carlo study

Monte Carlo simulations are used to calculate magnetic properties of two-dimensional layers of interacting nanoparticles (clusters) with random anisotropy. The model refers to thin granular antiferromagnetic films with net particle moments which are often encountered in exchange bias systems. The shape and the shift of hysteresis loops experimentally observed in metal oxide and metal oxide/ferromagnet systems can be reproduced by the interplay of two microscopic properties, the random anisotropy and the interparticle interaction. The existence of hysteresis turns out to be connected with spin-glass-like behavior. Random magnetic anisotropy of exchange-interacting nanoparticles (clusters) thus emerges as a new approach to the problem of exchange bias in granular (cluster) systems.