Comparison of a near-field ferromagnetic resonance probe with pump-probe characterization of CoCrPt media

Abstract

A near-field microwave technique is used to locally probe ferromagnetic resonance (FMR) in a series of CoCrPt alloys with varying perpendicular anisotropy (5 kOe< Hk <15 kOe). We observe broad FMR linewidths Δf on the order of a gigahertz and higher, indicating significant damping and sample inhomogeneities. These results are compared to time-domain measurements of the same samples using a pump-probe technique, where we observe relaxation times τ, considerably shorter than 500 ps, using a damped sinusoid to model the magnetization dynamics. We find the local FMR measurements to yield time scales consistent with the pump-probe data, using the Fourier relationship, Δf=1π τ. Thus, this near-field technique is capable of quantitative characterization of high-anisotropy and highly damped magnetic systems, something that has not been demonstrated before with a local FMR technique. © 2008 American Institute of Physics.