Influence of grain boundaries, interface roughness and non-collinear magnetic configurations in the AF layer on the exchange bias properties of F/AF nanodots: A numerical investigation

Motivated by the insufficient understanding of the drastic effects of the disordered interfacial phases at the interface in F/AF bilayers on the exchange bias properties, we consider a realistic model for F/AF nanodots which accounts for roughness at the interface, grain boundaries (GB) and magnetic frustration in the AF layer. Then, we investigate the effect of the magnetic disorder at the F/AF interface on the exchange field by means of Monte Carlo simulations. First, using a simplified model based on a perfect crystal structure (without GB) and with an ideal interface, our results indicate that non-collinear ordered magnetic configuration at the F/AF interface (due to frustration) causes a small decrease of the exchange field (about few dozen percent). Including GB in the model, we show that this kind of structural disorder produces disordered magnetic configurations with domains at the F/AF interface. This magnetic disorder does not lead to a decrease of the exchange field compared to the perfect crystal but makes the AF layer more stable. Our study also reveals that adding roughness in the form of a percentage of mixed F and AF moments in the interfacial layer results in a more significant decrease of the exchange field (two orders of magnitude) leading to values which are comparable to experimental values.