Temperature-dependent dynamic nuclear polarization of diamond

TL;DR

This study investigates how temperature influences dynamic nuclear polarization in diamond, revealing significant polarization enhancements at low temperatures and suggesting a hyperfine-mediated transfer mechanism.

Contribution

It provides the first detailed analysis of temperature-dependent DNP mechanisms in diamond, highlighting the role of hyperfine interactions over spin diffusion.

Findings

Polarization enhancements of 100 to 600 across temperatures

Strong temperature dependence of DNP profiles observed

Evidence for hyperfine-mediated polarization transfer mechanism

Abstract

Dynamic nuclear polarization (DNP) can increase nuclear magnetic resonance (NMR) signals by orders of magnitude. DNP in diamond proceeds through different DNP mechanisms with a possible temperature-dependence. We report on 13C dynamic nuclear polarization (DNP) experiments in diamonds at 3.4 T and 7 T between 300 K and 1.7 K. Nuclear polarization enhancements between 100 and 600 were measured for all temperatures, corresponding to polarizations at 7 T between 0.1% (300 K) and 38% (1.7 K). A strong temperature dependence of the DNP profiles was observed. Longitudinal-detected (LOD) electron paramagnetic resonance (EPR) experiments revealed an additional broad temperature-dependent electron line centered around the mI = 0 line of the P1 triplet transitions. Our results suggest that nuclei are preferentially polarized via a direct hyperfine mediated polarization transfer while spin diffusion in the sample plays a minor role.