Ferromagnetic Resonance Spectroscopy With Very Large Precession Cone Angle in Magnetic Tunnel Junctions

We have developed an experimental technique to electrically characterize ferromagnetic resonance (FMR) with a large precession cone angle by using magnetic tunnel junctions on a coplanar waveguide. We observed FMR of a Ni
₈₀
Fe
₂₀
layer as the tunneling resistance change capturing the angle between the Ni
₈₀
Fe
₂₀
precession magnetization and a fixed magnetization in a reference electrode. The resonant frequency shifts with increasing microwave power as a result of the large precession cone angle that reduces the effective anisotropy field. We confirmed the validity of our results by the numerical simulations based on the Landau- Lifshitz-Gilbert equation.