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Scalable microresonators for room-temperature detection of electron spin resonance from dilute, sub-nanoliter volume solids

Published

Author(s)

Nandita S. Abhyankar, Amit K. Agrawal, Pragya R. Shrestha, Russell A. Maier, Robert D. McMichael, Jason P. Campbell, Veronika A. Szalai

Abstract

Microresonators used for spin detection in volume-limited samples suffer from poor quality factors, which adversely affect sensitivity and ease of coupling to the microwave source. Here we adapt a metamaterial design with toroidal moment to confine microwave magnetic fields to picoliter volumes while increasing the quality factor by an order of magnitude. Using these planar inverse anapole microresonators, we obtain continuous (CW) wave electron paramagnetic resonance (EPR) spectra at 9 GHz and 34 GHz. We obtain a detection limit as low as 6 x 106 spins/(mT√Hz) (i.e. 6 x 105 spins/(G√Hz)) at room temperature, which is an improvement of an order of magnitude compared to previously reported microresonator designs for inductive- detection EPR. We show the broad applicability of these devices by incorporating them into existing commercial and homebuilt EPR spectrometers, replacing only the resonator and modulation coils in these systems.

Citation
Science Advances
Volume
6
Issue
44

Keywords

Electron paramagnetic resonance (EPR), microresonators, toroidal metamaterial

Citation

Abhyankar, N. , Agrawal, A. , Shrestha, P. , Maier, R. , McMichael, R. , Campbell, J. and Szalai, V. (2020), Scalable microresonators for room-temperature detection of electron spin resonance from dilute, sub-nanoliter volume solids, Science Advances, [online], https://doi.org/10.1126/sciadv.abb0620 (Accessed August 2, 2021)
Created October 27, 2020, Updated May 4, 2021