Development of Millimeter-Wave Fabry-Perot Resonator for Simultaneous Electron-Spin and Nuclear-Magnetic Resonance Measurement at Low Temperatures

We have developed millimeter-wave Fabry-Perot type resonator (FPR) aiming for simultaneous electron-spin and nuclear-spin resonance (ESR/NMR) measurements at very low temperatures below 1 K. The flat mirror of FPR is fabricated using a gold thin layer in order to minimize disturbance to radio frequency wave for NMR. An optimum thickness of the gold layer by measuring Q value is found. We have actually succeeded to detect both ESR and NMR at very low temperatures.