Vector network analyzer ferromagnetic resonance of thin films on coplanar waveguides: Comparison of different evaluation methods

Abstract

We have carried out two-port network analyzer ferromagnetic resonance measurements on a coplanar waveguide. We present a detailed description on how to calculate from the raw measurement data a value proportional to the complex susceptibility and permittivity of the ferromagnetic material. Necessary corrections for errors due to imprecise sample placement on the waveguide and the sample dimensions are presented. Evaluated data up to 15 GHz are provided for two model samples: a 40 nm Co80Fe20 layer showing a large linewidth (≈900 MHz) and a 40 nm Co72Fe18B10 layer yielding a small linewidth (≈360 MHz). Using these experimental data the presented evaluation scheme based on all four scattering parameters is then compared to commonly used approximate evaluation schemes relying on only one S parameter. These approximate methods show close agreement for the ferromagnetic resonance frequencies (the relative error is below 1%). However, the resonance linewidths show a relative error that can reach 10% in comparison with the presented evaluation method.

Strong asymmetry of microwave absorption by bilayer conducting ferromagnetic films in the microstrip-line based broadband ferromagnetic resonance

“…If one neglects the small contribution from the precessing magnetization to the total field, one can consider (8) as an inhomogeneous equation with the right-hand (driving) term in the form of the linear h x (y) function. This inhomogeneous system of differential equations can be easily solved analytically, but performing this is out of scope of this paper.…”

“…(12)(13)(14) as they are. But for nanometric metallic films and wide microstrip transducers Z r << 50Ω which is clearly seen in experiment as | Γ |<< 1 [8,36]. This allows considerable simplification of these formulas.…”

“…One of them is that of the effective microwave susceptibility [6,7,8]. It assumes that the total microwave energy absorbed by the material is lost due to magnetic losses by driven precession of magnetization in the area of localization of the microwave magnetic field of the transducer.…”

“…These setups are useful for accurately measuring spin wave excitations which are used as a probe for characterizing magnetic surfaces and buried interfaces. However, consideration needs to be made of the experimental setup when analyzing results [2,5,6,7,8,9]. In particular, Schneider et al [5] mention that measured response is dependent on the distance of the film from the coplanar surface due to a change in strip line impedance.…”

Ferromagnetic resonance linewidth reduction in Fe∕Au multilayers using ion beams

“…A detailed description of the measurement procedure is found elsewhere. 5 Varying the frequency of the small excitation field, the measured data allow the calculation of the dynamic susceptibility spectra of the sample. This is illustrated in Fig.…”