Effects of component ratio and easy axes distribution on the exchange bias in ferromagnetic-antiferromagnetic random alloys

For a ferromagnetic (FM)-antiferromagnetic (AFM) system with composition x(FM)+(AFM)_1−x, a modified Monte Carlo Metropolis method is performed to study the effects of x and easy axes distribution at the FM/AFM nearest neighbors on exchange bias field H_E, coercivity H_C, and vertical magnetization shift M_E after cooling under different magnetic fields h_CF. When the orientations of easy axes are uniform, the x dependence of H_E and M_E undergo a non-monotonous to monotonous process with the increase of h_CF, whereas H_C shows a more complex behavior. On the other hand, for the case of the random orientation, H_C has a peak around x=0.5, while M_E decreases with the increase of x. H_E exhibits negative extrema at small x and disappears for larger x. However, abnormal positive H_E observed depends on the frustration and the distinct trends of two coercive fields with x in such a special model.