Microwave-free imaging magnetometry with nitrogen-vacancy centers in nanodiamonds at near-zero field

TL;DR

This paper introduces a microwave-free, wide-field imaging magnetometer using NV centers in nanodiamonds that operates at near-zero magnetic fields, enabling magnetic sensing without microwave interference in biological and conductive samples.

Contribution

It demonstrates a novel microwave-free NV-based magnetometry technique utilizing zero-field cross-relaxation in nanodiamonds under ambient conditions.

Findings

Achieved a sensitivity of 4.5 μT/√Hz.

Demonstrated magnetic imaging without microwaves in nanodiamonds.

Operates effectively at near-zero magnetic fields.

Abstract

Magnetometry using Nitrogen-Vacancy (NV) color centers in diamond predominantly relies on microwave spectroscopy. However, microwaves may hinder certain studies involving biological systems or thin conductive samples. This work demonstrates a wide-field, microwave-free imaging magnetometer utilizing NV centers in nanodiamonds by exploiting the cross-relaxation feature near zero magnetic fields under ambient conditions without applying microwaves. For this purpose, we measure the center shift, contrast, and linewidth of the zero-field cross-relaxation in 140 nm nanodiamonds drop-cast on a current-carrying conductive pattern while scanning a background magnetic field, achieving a sensitivity of 4.5 $\mathrm{\mu T/\sqrt{Hz}}$. Our work allows for applying the NV zero-field feature in nanodiamonds for magnetic field sensing in the zero and low-field regimes and highlights the potential for microwave-free all-optical wide-field magnetometry based on nanodiamonds.