Microwave frequency modulation in continuous-wave far-infrared ESR utilizing a quasi-optical reflection bridge.
We report the development of the frequency-modulation (FM) method for measuring electron spin resonance (ESR) absorption in the 210- to 420GHz frequency range. We demonstrate that using a high-frequency ESR spectrometer without resonating microwave components enables us to overcome technical difficulties associated with the FM method due to nonlinear microwave-elements, without sacrificing spectrometer performance. FM was achieved by modulating the reference oscillator of a 13GHz Phase-Locked Dielectric Resonator Oscillator, and amplifying and frequency-multiplying the resulting millimeter-wave radiation up to 210, 315 and 420GHz. ESR spectra were obtained in reflection mode by a lock-in detection at the fundamental modulation frequency, and also at the second and third harmonic. Sensitivity of the setup was verified by conduction electron spin resonance measurement in KC60.
Náfrádi
Bálint
B
Institute of Physics of Complex Matter, FBS, Swiss Federal Institute of Technology (EPFL), PH D3 315 (Batiment PH) Station 3, CH-1015 Lausanne, Switzerland. balint.nafradi@epfl.ch <balint.nafradi@epfl.ch>
Gaál
Richard
R
Fehér
Titusz
T
Forró
László
L