Combined excitation of an optically detected magnetic resonance in nitrogen-vacancy centers in diamond for precision measurement of the components of a magnetic field vector

We used synchronous radio-frequency excitation of three components of a hyperfine resonance line in the scheme of the vector sensor of a magnetic field based on optically detected magnetic resonance in the nitrogen-vacancy centers in diamond crystal. As a result, for the first time, the sensitivity of order 1.5 nT Hz$^{-1/2}$ in the frequency range of 0–100 Hz was reached in the crystal with a volume of 0.01 mm$^3$ glued to the end of an optical fiber.