13C spin–lattice relaxation in natural type-IIb semiconducting diamond

13C Spin–Lattice Relaxation in Natural Diamond: Zeeman Relaxation in Fields of 500 to 5000 G at 300 K Due to Fixed Paramagnetic Nitrogen Defects

“…Several NMR studies [1][2][3][4][5] of natural and synthetic diamonds have revealed a wide range (1 s to several days) of 13 C laboratory frame spin-lattice relaxation (SLR) times (T 1 ) at high magnetic fields. In natural type I and IIa diamonds the fixed paramagnetic impurity nuclear relaxation mechanism [6][7][8][9][10][11], including nuclear spin diffusion, is dominant at high fields [2].…”

“…In natural type I and IIa diamonds the fixed paramagnetic impurity nuclear relaxation mechanism [6][7][8][9][10][11], including nuclear spin diffusion, is dominant at high fields [2]. The contribution of the nuclear relaxation mechanism [12], by which thermal lattice vibrations induce transitions in the 13 C nuclear spin system via modulation of the nuclear dipole-dipole interactions, is negligibly small, even for 99% 13 C-enriched diamond [5]. For natural type IIb semiconducting diamond the 13 C SLR mechanism is completely different and involves mobile hole carriers [13].…”

“…Three different nuclear SLR paths, namely that due to electron SLR and two types of three spin processes, are discussed. The one three-spin process (TSP) (type 1) involves a simultaneous transition of two electron spins belonging to the same hyperfine EPR line and a 13 C spin while the other process (type 2) involves two electron spins belonging to different hyperfine EPR lines and a 13 C spin. It is shown that the thermal contact between the 13 C nuclear Zeeman and electron dipole-dipole interaction reservoirs decreases with an increase in field intensity, thus forming a bottleneck in the 13 C relaxation path due to the type 1 TSP.…”

“…The one three-spin process (TSP) (type 1) involves a simultaneous transition of two electron spins belonging to the same hyperfine EPR line and a 13 C spin while the other process (type 2) involves two electron spins belonging to different hyperfine EPR lines and a 13 C spin. It is shown that the thermal contact between the 13 C nuclear Zeeman and electron dipole-dipole interaction reservoirs decreases with an increase in field intensity, thus forming a bottleneck in the 13 C relaxation path due to the type 1 TSP. The contribution of TSP of type 1 dominates that due to electron SLR and the type 2 TSP in relaxing the 13 C nuclei in type Ib diamond from about 1200 to 5000 G, while for type Ia diamond it dominates from 500 up to about 2200 G. In type Ia diamond over the range 2200 to 5000 G it seems that the type 2 TSP, which involves electrons of neighboring P2 hyperfine lines, dominates that of electron spin-lattice and the type 1 TSP.…”

“…It is shown that the thermal contact between the 13 C nuclear Zeeman and electron dipole-dipole interaction reservoirs decreases with an increase in field intensity, thus forming a bottleneck in the 13 C relaxation path due to the type 1 TSP. The contribution of TSP of type 1 dominates that due to electron SLR and the type 2 TSP in relaxing the 13 C nuclei in type Ib diamond from about 1200 to 5000 G, while for type Ia diamond it dominates from 500 up to about 2200 G. In type Ia diamond over the range 2200 to 5000 G it seems that the type 2 TSP, which involves electrons of neighboring P2 hyperfine lines, dominates that of electron spin-lattice and the type 1 TSP. Over the range 500 to about 1200 G, a field-dependent electron SLR…”