Temperature Dependence of the Nitrogen-Vacancy Magnetic Resonance in Diamond

The temperature dependence of the magnetic-resonance spectra of nitrogen-vacancy (${\mathrm{NV}}^{\ensuremath{-}}$) ensembles in the range of 280--330 K was studied. Four samples prepared under different conditions were analyzed with ${\mathrm{NV}}^{\ensuremath{-}}$ concentrations ranging from 10 ppb to 15 ppm. For all samples, the axial zero-field splitting (ZFS) parameter $D$ was found to vary significantly with temperature, $T$, as $dD/dT=\ensuremath{-}74.2(7)\text{ }\text{ }\mathrm{kHz}/\mathrm{K}$. The transverse ZFS parameter $E$ was nonzero (between 4 and 11 MHz) in all samples, and exhibited a temperature dependence of $dE/(EdT)=\ensuremath{-}1.4(3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }{\mathrm{K}}^{\ensuremath{-}1}$. The results might be accounted for by considering local thermal expansion. The temperature dependence of the ZFS parameters presents a significant challenge for diamond magnetometers and may ultimately limit their bandwidth and sensitivity.