Calculation of spin wave mode response induced by a coplanar microwave line

The geometry and method of spin wave excitation in planar waveguide inductive resonance methods is very different from that used in resonant cavity experiments, and correct interpretation of results requires an analysis which takes into account a number of features associated with the use of broadband microwave experiments. We consider aspects of a theoretical description of the resonance modes in ferromagnetic multilayers measured by a broadband inductive technique in a coplanar waveguide geometry. The effects of finite conductivity of the magnetic sample and contributions to the measured response from finite wavelength spin waves excited in this geometry are discussed. We also include the screening action of the coplanar line on the spin wave dispersion in the theory. We show that for a proper description of intensities, the theoretical model for the spin wave excitation has to include not only the contribution to intensities from the microwave current in the central conductor as did previous theories but also contributions from reverse currents in the ground half-planes of the coplanar waveguide.