Is the magnetic moment of the neutron a dipole or an Amperian current loop?

Abstract

In classical electrodynamics the two model representations of magnetic moments, viz. the dipole and the Amperian current loop models, give equivalent results. In contrast, for particles with overlapping wave functions, this equivalence breaks down. In the case of the neutron a heated theoretical debate in the 1930’s on the choice of the correct model has been experimentally settled in the 1950’s in favour of the current loop model. The question became of down-to-earth technical relevance in neutron spin echo spectroscopy.