Low-field optically detected magnetic resonance of a coupled triplet-doublet defect pair in diamond.

Microwave-induced changes in the optical emission of the NV center in diamond have previously been attributed to magnetic resonance of the defect in its A ground state [E. van Oort et al. , J. Phys. C 21, 4385 (1988)]. In this paper, the focus is on the origin of the hyperfine splittings that are observed in the optically detected magnetic-resonance (ODMR) spectra at zero and low magnetic fields. Detailed analysis of the anisotropic behavior of the line splittings in a magnetic field shows that the hyperfine structure arises from triplet-doublet magnetic dipolar interactions of NV centers and P] centers (with S = —, ' ). The ODMR spectrum of the N-V center appears to display the nitrogen hyperfine interaction characteristic of the P] center.