Double electron-electron resonance for investigation spin bath in diamond

NV-centers in diamonds are promising sensors of magnetic fields due to the possibility to control their state optically. The coherence of NV centers in diamond is limited by other paramagnetic impurities - C-centers. Unlike the NV- center, the C-center is a dark defect. This work demonstrates the detection, state control, and concentration determination of C-centers through their interaction with NV-centers.