Exchange Bias with Interacting Random Anti-ferromagnetic Grains
  A model consisting of random interacting anti-ferromagnetic (AF) grains coupled to a ferromagnetic (FM) layer is developed to study the exchange bias phenomenon. This simple model is able to describe several exchange bias behavior observed in real materials. Shifts in hysteresis loops are observed as a function of cooling field and average grain size. We establish a direct relationship between cooling field dependence of exchange bias, coercivity and magnetization state on the AF-FM interface. We also verify that the exchange bias field is inversely proportional to the grain size, and this behavior is independent of the inter-grain interactions, AF/FM coupling and cooling field. 
Hwee Kuan Lee and Yutaka Okabe