Rotatable anisotropy of Ni81Fe19/Ir20Mn80 films: A study using broadband ferromagnetic resonance

Abstract We investigate the broadband ferromagnetic resonance dispersion relation of NiFe/IrMn multilayers using the vector network analyzer ferromagnetic resonance (VNA-FMR) method. Multilayered films with structure [NiFe(20 nm)/IrMn ( t IrMn )/Ta(3 nm)]×10 (with t IrMn =4 and 15 nm) were produced onto Si(100) substrates using magnetron sputtering. The dispersion relations of the samples were extracted from the resonance spectra in the range of 0.1–7 GHz under magnetic fields of up to±300 Oe. Static magnetization curves were also obtained in the same field range. The experimental data were compared with numerical calculations performed using the granular exchange-bias model which takes into account both, the unidirectional and rotatable anisotropy present in the samples. A good agreement between numerical and experimental results was achieved without the need of any frequency or field-dependent parameter.