Understanding the Line Shape of Ferromagnetic Resonance Spectrum in a Flip-Chip Measurement

Flip-chip ferromagnetic resonance spectrum with a coplanar waveguide has been widely used for studying magnetization dynamics of thin films. Typically, the peak position and linewidth are extrapolated, while the line shape — specifically how far the spectrum deviates from a perfectly symmetric Lorentzian — is neglected. To quantify this deviation, we define a deviation phase angle (DPA), and we find that the DPA of the ferromagnetic resonance spectrum depends on frequency, impedance mismatch in the transmission line, as well as the material itself.