Determination of exchange and rotational anisotropies in IrMn/Fe(t)/IrMn exchange coupled structures using dynamic and static techniques:: Application to microwave devices

We determined the exchange anisotropy and rotational anisotropy of IrMn(7 nm)/Fe(t=3-20 nm)/IrMn(7 nm) exchange-biased structures using conventional ferromagnetic resonance (FMR) and network analyzer FMR (NA-FMR). Compared to single Fe layer films of identical thickness, we observe an isotropic downward shift and an angular variation of the FMR resonance field in the multilayer structures. The isotropic shift originates from the rotational anisotropy, while the angular variation originates from the exchange anisotropy. Both exchange anisotropy and rotational anisotropy increase with decreasing Fe thickness in the exchange-biased structures. The isotropic downward shift of the resonance field translates to an upward shift of the resonance frequency, and can be used to boost the operational frequency of microwave devices (bandpass/stop filters) by several gigahertz. (c) 2008 American Institute of Physics.