Researchers at NIST have developed a new type of microresonator called a “planar inverse anapole” that significantly improves the sensitivity of electron paramagnetic resonance (EPR) spectrometry. The key innovation is the use of anapole structures to confine microwave magnetic fields to extremely small volumes (picoliters), while also minimizing radiative losses that reduce sensitivity.
The new microresonator design achieves an order of magnitude improvement in sensitivity compared to previous designs, with a spin detection limit as low as 6 x 10^6 (mT√Hz)-1 at 10 GHz and room temperature. This high sensitivity is enabled by the device’s high quality-factor, which allows easy coupling to microwave feedlines for continuous wave (CW) EPR experiments.
The planar inverse anapole microresonator is scalable to microwave frequencies above 100 GHz, opening the door to multifrequency EPR measurements on volume-limited samples. The design is also compatible with existing spectrometer setups, enabling routine measurements of picoliter-volume samples with improved sensitivity.
Keywords: Anapole, Microresonator, Electron Spins, Spin Detection, Microwave Frequencies
