A weak magnetic field sensor based on nitrogen-vacancy color centers in a diamond crystal

The effect of magnetically dependent absorption of radio-frequency high-frequency radiation detected by the method of optically detected magnetic resonance has been studied, and an explanation for it is proposed. A method of high-frequency excitation of optically detected magnetic resonance in nitrogen-vacancy color centers in a diamond crystal has been experimentally studied that provides magnetometric sensitivity at the level of units of nanoteslas in the 1-Hz band in zero and weak ($<$ 0.1 mT) magnetic fields. The method does not involve the use of microwave fields, which makes it attractive for biological and medical applications, primarily for tasks of invasive magnetoencephalography.