Unraveling the magnetic coupling in the interface of the exchange-biased IrMn/permalloy multilayers

摘要

The magnetic properties of a series of IrMn(Ir38Mn68)/permalloy (Ni80Fe20) exchange-biased films are investigated using X-ray magnetic circular dichroism (XMCD). The ferromagnetic permalloy films in different samples are of the same thickness (5 nm) while the antiferromagnetic IrMn films have various thickness between 15 and 40 nm. The exchange-field and coercivity is observed to increase with IrMn thickness. XMCD spectra are used to obtain the magnetic moments. It is shown that when the thickness of IrMn layer increases from 20 to 30 nm, a significant increase of the Fe spin-moment occurs. However, the spin-moment of Ni shows no obvious change. We argue that this effect is attributed to the strong coupling between Fe and Mn, while the coupling between Ni and Mn is relatively weaker. The results show the importance of understanding magnetic coupling effects at the exchange-biased FM/AFM interfaces. The study of these interfacial effects can potentially pave the way to the future development of spin-valve devices.