Spin Relaxometry with Solid-State Defects: Theory, Platforms, and Applications

TL;DR

This paper reviews how solid-state spin defects, especially NV centers, are used as sensitive probes for environmental noise, enabling applications in sensing and spectroscopy by analyzing spin relaxation rates.

Contribution

It provides a comprehensive theoretical and experimental overview of spin relaxometry, clarifying the relationship between relaxation rates and noise spectra, and discusses diverse applications and future challenges.

Findings

Spin relaxometry effectively probes magnetic noise spectra.

The geometry of the sensor influences measurement sensitivity.

Applications span condensed matter, chemistry, biology, and magnetic resonance.

Abstract

Spin relaxometry using solid-state spin defects, such as the diamond nitrogen-vacancy (NV) center, probes dynamical processes by measuring how environmental fluctuations enhance the spin relaxation rate. In the weak-coupling limit, relaxation rates sample the transverse magnetic-noise power spectral density through a sensor-specific filter function, turning the defect into a local, frequency-selective noise spectrometer. This review bridges theory and experiment, clarifying how measured relaxation rates map onto noise spectra and how near-field geometry shapes the response. We highlight representative applications across condensed-matter physics, chemical and biological sensing, and relaxometry-based magnetic-resonance spectroscopy. We conclude with emerging opportunities and key challenges.