Researchers at NIST have developed a new type of microresonator that can detect electron spin resonance in very small sample volumes at room temperature. The key innovation is a metamaterial design with toroidal moment that confines microwave magnetic fields to picoliter volumes while increasing the quality factor by an order of magnitude.
This allows for continuous wave (CW) electron paramagnetic resonance (EPR) spectra to be obtained at 9 GHz and 34 GHz frequencies. The detection limit is improved by an order of magnitude compared to previous microresonator designs, reaching as low as 6 x 10^6 spins/(mT√Hz) or 6 x 10^5 spins/(G√Hz) at room temperature.
The new microresonators have been successfully incorporated into both commercial and homebuilt EPR spectrometers, demonstrating their broad applicability and ease of integration. This advancement could enable more sensitive and efficient EPR measurements in various scientific and technological applications.
Keywords: quality factor, spin detection, microwave magnetic fields, electron paramagnetic resonance, microresonators
