Electron spin resonance spectroscopy of small ensemble paramagnetic spins using a single nitrogen-vacancy center in diamond

TL;DR

This paper demonstrates electron spin resonance spectroscopy using a single nitrogen-vacancy center in diamond to detect and analyze nanoscale bath spins, identifying nitrogen impurities and estimating the number of detectable spins.

Contribution

It introduces a method for ESR spectroscopy at the single NV center level, enabling nanoscale magnetic sensing and characterization of individual spin environments.

Findings

Identified nitrogen impurity spins as major paramagnetic centers.

Demonstrated NV-based ESR spectrum measurement of bath spins.

Estimated the number of detectable spins to be less than or equal to 50.

Abstract

A nitrogen-vacancy (NV) center in diamond is a promising sensor for nanoscale magnetic sensing. Here we report electron spin resonance (ESR) spectroscopy using a single NV center in diamond. First, using a 230 GHz ESR spectrometer, we performed ensemble ESR of a type-Ib sample crystal and identified a substitutional single nitrogen impurity as a major paramagnetic center in the sample crystal. Then, we carried out free-induction decay and spin echo measurements of the single NV center to study static and dynamic properties of nanoscale bath spins surrounding the NV center. We also measured ESR spectrum of the bath spins using double electron-electron resonance spectroscopy with the single NV center. The spectrum analysis of the NV-based ESR measurement identified that the detected spins are the nitrogen impurity spins. The experiment was also performed with several other single NV centers in the diamond sample and demonstrated that the properties of the bath spins are unique to the NV centers indicating the probe of spins in the microscopic volume using NV-based ESR. Finally, we discussed the number of spins detected by the NV-based ESR spectroscopy. By comparing the experimental result with simulation, we estimated the number of the detected spins to be $\leq$ 50 spins.