Precision microwave dielectric and magnetic susceptibility measurements of correlated electronic materials using superconducting cavities
arXiv:cond-mat/0001280 · doi:10.1063/1.1305519
Abstract
We analyze microwave cavity perturbation methods, and show that the technique is an excellent, precision method to study the dynamic magnetic and dielectric response in the $GHz$ frequency range. Using superconducting cavities, we obtain exceptionally high precision and sensitivity for measurements of relative changes. A dynamic electromagnetic susceptibility $\tildeζ(T)=ζ^{\prime}+iζ^{\prime \prime}$ is introduced, which is obtained from the measured parameters: the shift of cavity resonant frequency $δf$ and quality factor $Q$. We focus on the case of a spherical sample placed at the center of a cylindrical cavity resonant in the $TE_{011}$ mode. Depending on the sample characteristics, the magnetic permeability $\tildeμ$, the dielectric permittivity $\tildeε$ and the complex conductivity $\tildeÏ$ can be extracted from $\tildeζ_{H}$. A full spherical wave analysis of the cavity perturbation is given. This analysis has led to the observation of new phenomena in novel low dimensional materials.
16 pages, 5 figures