Observation of the Nuclear Barnett Effect

Abstract

We have made the first observation of the nuclear Barnett effect. In the electronic Barnett effect, which was first observed in 1915 by Samuel Barnett, a ferromagnetic rod was spun about its long axis and a magnetization developed in the rod along the axis of rotation. This effect is caused by the coupling between the angular momentum of the electronic spins in the sample and the rotational motion of the rod. In our experiment, we measured the nuclear Barnett effect by rotating a sample of water at rotational speeds up to 13.5 kHz in a weak magnetic field and observed a change in the polarization of the protons in the sample that is proportional to the frequency of rotation. We measured this polarization by observing the change in the size of a nuclear magnetic resonance (NMR) signal. No NMR frequency shift was observed due to rotation, meaning that this magnetization was not produced by a real magnetic field.