Inversion of the EPR signal from P1 centers in a synthetic diamond single crystal under normal conditions

The electron paramagnetic resonance (EPR) spectrum of a synthetic 0.15-carat diamond single crystal grown in a (Fe-Co-C) system using the temperature gradient method in a split-sphere type apparatus has been studied. It is established that the EPR signal from P1 centers (representing nitrogen atoms occurring at the C sites) present in the diamond crystal upon a high-temperature high-pressure (HTHP) treatment exhibits inversion when the microwave power in an H-102 resonator is increased from 70 mu W to 70 mW at a polarizing magnetic field scan rate from 0.5 to 5 mT/min. No such inversion is observed in the initial diamond (before the HTHP treatment).