Kavtanyuk, Vladimir Vladimirovich, Changjae Lee, Keunhong Jeon, and Jeong Hyun Shim. “Achieving 5% 13C Nuclear Spin Hyperpolarization in High-Purity Diamond at Room Temperature and Low Magnetic Field,” November 25, 2024.
https://doi.org/10.21203/rs.3.rs-5319138/v1.
Optically polarizable nitrogen-vacancy (NV) centers in diamond enable hyperpolarization of 13C nuclear spins at a low magnetic field and room temperature. However, it remains a challenge to achieve a high level of polarization, comparable to that of conventional dynamic nuclear polarization. In this paper, we demonstrate that a 13C polarization of 5% can be attained at less than 10 mT, equivalent to an enhancement ratio of over 7 × 106. We used a high-purity diamond with an initial nitrogen concentration below 1 ppm, resulting in a storage time exceeding 100 minutes. Aligning the magnetic field along [100] increased the number of NV spins involved in polarization transfer by a factor of four. For this field orientation, a comprehensive optimization of the field intensity and microwave (MW) frequency-sweep parameters has been performed. The optimum MW sweep width suggests that polarization transfer occurs primarily to the bulk 13C spins through the integrated solid effect, followed by nuclear spin diffusion.