  High-spin defect centers in crystal matrices are used in quantum computing
technologies, highly sensitive sensors, and single-photon sources. In this
work, optically active nitrogen-vacancy color centers NV in a 28Si-enriched
(nuclear spin I = 0) 6H-28SiC crystal have been studied using the photoinduced
(980 nm) high-frequency (94 GHz, 3.4 T) pulsed electron paramagnetic resonance
method at a temperature of 150 K. Three structurally nonequivalent types of NV-
centers with axial symmetry have been identified and their spectroscopic
parameters have been determined. Long spin-lattice, T1=1.3 ms, and spin-spin,
T2=59 us, ensemble relaxation times of NV- centers with extremely narrow (450
kHz) absorption lines allow highly selective excitation of resonant transitions
between sublevels caused by the weak hyperfine interaction (A = 1 MHz) with 14N
(I = 1) nuclei for the quantum manipulation of the electron spin magnetization.
