Electron magnetic resonance Fermi surface imaging: Applications to organic conductors and Sr₂RuO₄

We report detailed angle dependent studies of the metallic state microwave (40 to 200 GHz) magneto-conductivity of single crystal samples of the α-(BEDT-TFF)₂KHg(SCN)₄ organic charge density wave conductor, and the perovskite superconductor Sr₂RuO₄. We observe series' of resonant absorptions which we attribute to periodic orbit resonances - a phenomenon closely related to cyclotron resonance. By performing measurements on several samples, and in different electromagnetic field configurations, we are able to couple to different orbital modes (+ harmonics), which derive from deformations (warpings) of the quasi-one and quasi-two-dimensional Fermi surfaces of these compounds. These studies provide vital information concerning interlayer dispersion which, in turn, affects the Fermi surface nesting characteristics which are believed to play a crucial role in the low temperature physics of these exotic materials.