Scalar Magnetic Field Measurement Based on Nitrogen-Vacancy Centers in Diamond

Nitrogen-vacancy (NV) centers in diamond have emerged as promising platforms for quantum magnetic field measurement. Conventional NV-based magnetometry requires precise alignment with field orientation, fundamentally limiting its applicability in unconstrained measurement scenarios. In this article, we present an orientation-independent scalar magnetometry technique exploiting the zero-field splitting (ZFS) characteristics of NV ensembles under optically detected magnetic resonance (ODMR) with high stability. We demonstrate a scalar magnetometry system capable of wide-range measurement from 2 mT to 45 mT. By employing a strategy that combines segmented measurement with independent fitting of individual ODMR spectral lines, the system achieves enhanced measurement stability with significantly improved measurement effciency. A field-programmable gate array (FPGA)-based pulse generating and data acquisition system and a Python automated analysis program are implemented in this work. Experimental validation demonstrates the measured magnitude has the maximum ± 0.461 % deviation from the reference magnetic field by a standard field generator, with nonlinearity error of 0.0952 % in the range mentioned above and measurement noise figure of 359.58 nT/ √ Hz. This orientation-insensitive approach establishes a new paradigm for non-invasive magnetic measurements, particularly suitable for biomedical diagnostics requiring anatomical adaptability and industrial inspection of complex component geometries.