Magnetometer and method for finding a magnitude of an ambient magnetic field or of one or more components thereof

A magnetometer that finds a magnitude of an ambient magnetic field or of one or more components of the magnetic field or both, comprising:

• a) a crystal having a diamond cubic structure with four tetrahedral axes, with an ensemble of paramagnetic defects, some of the defects oriented along each of the crystal's four tetrahedral axes;
• b) a microwave source that produces a microwave field at the crystal of controllable frequency over a range that includes microwave resonance frequencies, in the presence of the ambient magnetic field, for paramagnetic defects oriented along all four axes;
• c) a light source with a light emitting surface that illuminates the paramagnetic defects with light of a wavelength to cause fluorescent emission;
• d) a light detector with a light detecting surface, that measures a total detected power of fluorescent emission light of the paramagnetic defects;
• and
• e) a controller configured to:
• 1) measure the detected fluorescent emission power at each of a plurality of different selected microwave frequencies within the range, over a spectrum acquisition time, to obtain a spectrum of the paramagnetic defect ensemble;
• and
• 2) calculate the magnitude of the magnetic field or the one or more components of the magnetic field or both, from the spectrum;
• wherein all of the crystal is closer to the light emitting surface than a largest transverse dimension of the light emitting surface, and closer to the light detecting surface than a largest transverse dimension of the light detecting surface.

A method of determining a magnitude of an ambient magnetic field, using an ensemble of paramagnetic defects in a crystal having a diamond cubic structure with four tetrahedral axes, some of the defects oriented along each of the crystal's four tetrahedral axes, the defects having a zero-field splitting resonant frequency Do, the method comprising:

• a) exposing the paramagnetic defect ensemble to microwave radiation at a selected frequency;
• b) illuminating the paramagnetic defects with light, from a light source, of a wavelength to cause fluorescent emission;
• c) measuring a total detected fluorescent emission power from the paramagnetic defect ensemble with a light detector;
• d) repeating (a), (b) and (c), using different selected frequencies of the microwave radiation to obtain a microwave absorption spectrum of the paramagnetic defect ensemble over frequencies that include Zeeman splitting of the zero-field splitting resonant frequency Do, due to the ambient magnetic field, for paramagnetic defects oriented along all four tetrahedral axes;
• e) calculating a variance property of the microwave absorption spectrum;
• and
• f) calculating a magnitude of the ambient magnetic field from the variance property.