Weak Magnetic Field Resonance Effects in Diamond with Nitrogen-Vacancy Centers

The photoluminescence intensity of the ensemble of NV centers in diamond at weak magnetic field was studied. Two resonances were revealed in the region of weak magnetic fields: the first resonance with a width of the order of 20 G, and the second resonance with a width of the order of 180 G. The presence of these optical resonances makes it possible to propose a new concept for creating magnetic field sensors based on a diamond with an ensemble of NV centers without the use of a microwave field.