Magnetic Properties of Exchange-Biased $[{\rm Co/Pt}]_{\rm n}$ Multilayer With Perpendicular Magnetic Anisotropy

Perpendicular exchange-biased [Co/Pt]₃/Co(t_Co)/IrMn andIrMn/Co(t_Co)/Pt/[Co/Pt]₃ multilayers have been fabricated, changing the thickness (t_Co) of the cobalt that is next to the IrMn layer. The crystal structure, interface roughness and magnetic properties were characterized by X-ray diffraction (XRD), X-ray reflectivity (XRR), atomic force microscopy (AFM) and extraordinary Hall Effect (EHE). The multilayers are flat, and the roughness is about 0.2 nm across the 2-¿m scanning range. The magnetization reversal is dependent on t_Co, and the exchange bias and coercivity vary with t_Co. The exchange bias reaches a maximum value (about 13.9 mT) for top-pinned multilayers at t_Co = 0.45 nm, while it reaches a maximum (about 3.5 mT) for bottom-pinned multilayers at t_Co = 0.6 nm. For both stacks the coercivity is maximum (about 30 mT) at t_Co = 0.8 nm, and stable for t_Co > 1.0 nm. These results are well understood in terms of the Co spin orientation at the Co/IrMn interface.