Temperature-scanned magnetic resonance and the evidence of two-way transfer of a nitrogen nuclear spin hyperfine interaction in coupled NV–N pairs in diamond

New method for the detection of magnetic resonance signals versus temperature is developed on the basis of the temperature dependence of the spin Hamiltonian parameters of the paramagnetic system under investigation. The implementation of this technique is demonstrated on the nitrogen-vacancy (NV) centers in diamonds. Single NV defects and their ensembles are suggested to be almost inertialess temperature sensors. The hyperfine structure of the $^{14}$N nitrogen nuclei of the nitrogen-vacancy center appears to be resolved in the hyperfine structure characteristic to the hyperfine interaction between NV and N$_{s}$ center (substitutional nitrogen impurity) in the ODMR spectra of the molecular NV–N$_{s}$ complex. Thus, we show that a direct evidence of the two-way transfer of a nitrogen nuclear spin hyperfine interaction in coupled NV–N$_{s}$ pairs was observed. It is shown that more than 3-fold enhancement of the NV ODMR signal can be achieved by using water as a collection optics medium.