Acoustic Nuclear Magnetic Resonance in Antiferromagnetic Insulators

Abstract

A proposal of phonon-induced nuclear magnetic resonance in antiferromagnetic insulators has been considered theoretically. We have found that such an experiment can serve as an extremely useful tool to measure properties such as the phenomenological coupling constant associated with the one phonon-one magnon magnetoelastic coupling. The mechanism with which the coherent lattice energy is absorbed by the nuclear spin system is a two-step process in which a phonon first excites a virtual spin wave via the magneto-elastic coupling and then a nuclear spin is flipped through the decay of the virtual spin wave via the off-diagonal matrix elements of electron-nuclear hyperfine interaction. The resulting attenuation coefficient is proportional to the square of the phenomenological coupling constant. This then remains the only unknown parameter, presuming that the hyperfine coupling constant has been predetermined by conventional micro-wave nuclear magnetic resonance. The order-of-magnitude estimates indicate that the effect should be well within the experimentally observable region.