A magnetic field is predicted to emerge on a particle in a rotating material body even if the body is electrically neutral. This emergent field is called a Barnett field. We show that nuclear magnetic resonance (NMR) enables direct measurement of the Barnett field in solids. We rotated both a sample and an NMR coil synchronously at high speed and found an NMR shift whose sign reflects that of the nuclear magnetic moments. This result provides direct evidence of the Barnett field. The use of NMR for Barnett field measurement enables the unknown signs of nuclear magnetic moments in solids to be determined.
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