Nuclear quadrupole resonance spectroscopy with a femtotesla diamond magnetometer

Abstract

Radio frequency (RF) magnetometers based on nitrogen vacancy centers in diamond are predicted to offer femtotesla sensitivity, but previous experiments were limited to the picotesla level. We demonstrate a femtotesla RF magnetometer using a diamond membrane inserted between ferrite flux concentrators. The device provides ~300-fold amplitude enhancement for RF magnetic fields from 70 kHz to 3.6 MHz, and the sensitivity reaches ~70 fT√s at 0.35 MHz. The sensor detected the 3.6-MHz nuclear quadrupole resonance (NQR) of room-temperature sodium nitrite powder. The sensor’s recovery time after an RF pulse is ~35 μs, limited by the excitation coil’s ring-down time. The sodium-nitrite NQR frequency shifts with temperature as −1.00±0.02 kHz/K, the magnetization dephasing time is T 2 *=887±51 μs, and multipulse sequences extend the signal lifetime to 332±23 ms, all consistent with coil-based studies. Our results expand the sensitivity frontier of diamond magnetometers to the femtotesla range, with potential applications in security, medical imaging, and materials science.

Compact and Fully Integrated LED Quantum Sensor Based on NV Centers in Diamond

“…In recent years, negatively charged NV centers in diamond have become established in the field of quantum-based sensing. NV centers can be used to build highly sensitive magnetic field sensors even in the fT/ √ Hz range [1][2][3]. These can be kept extremely small with spatial resolutions down to atomic size [4][5][6][7].…”

“…The decay of electrons in the m s = 0 spin state leads to fluorescence with a dominant wavelength of 637 nm, while the m s = ±1 state has a higher probability of non-radiative transitions to the 1 A 1 singlet state. Manipulation of the electron spin state with microwave magnetic field resonant to the electron spin transitions in the ground state 3 A 2 will therefore decrease the fluorescence emitted by the NV center.…”