Temperature and magnetic field dependent longitudinal spin relaxation in nitrogen-vacancy ensembles in diamond

TL;DR

This study investigates how temperature and magnetic fields influence the electron-spin relaxation time (T1) in nitrogen-vacancy ensembles in diamond, revealing multiple relaxation processes and their dependencies.

Contribution

It provides a comprehensive experimental analysis of T1 relaxation mechanisms across a wide temperature and magnetic field range in NV diamond ensembles, identifying three distinct processes.

Findings

Two-phonon Raman process dominates above room temperature.

An Orbach-type process with a specific activation energy is observed at lower temperatures.

T1 can be tuned by magnetic field, varying by more than an order of magnitude.

Abstract

We present an experimental study of the longitudinal electron-spin relaxation time (T1) of negatively charged nitrogen-vacancy (NV) ensembles in diamond. T1 was studied as a function of temperature from 5 to 475 K and magnetic field from 0 to 630 G for several samples with various NV and nitrogen concentrations. Our studies reveal three processes responsible for T1 relaxation. Above room temperature, a two-phonon Raman process dominates, and below, we observe an Orbach-type process with an activation energy, 73(4) meV, which closely matches the local vibrational modes of the NV center. At yet lower temperatures, sample dependent cross relaxation processes dominate, resulting in temperature independent values of T1, from ms to minutes. The value of T1 in this limit depends sensitively on magnetic field and can be tuned by more than an order of magnitude.