Magnetic Interaction between Neutrons and Electrons

Abstract

The phenomenological interaction operator between neutrons and electrons is usually assumed to be -$\mu \mathbf{s}$·B. ($\mu \mathbf{s}$ magnetic moment of the neutron, B magnetic field of the electrons.) Bloch has pointed out that other operators are possible. It is shown that the class of operators considered by Bloch is equivalent with the form -$\mu \mathbf{s}$·($\mathbf{H}+4\mathrm{}\pi C\mathbf{M}$) where M is the spin momentum density of the electrons, $\mathbf{H}=\mathbf{B}-4\mathrm{}\pi \mathbf{M}$ and $C$ is an indeterminate constant. Diffraction by ferromagnetic crystals and magnetic double refraction are calculated for this interaction. Present experimental evidence excludes the value $C=0\mathrm{}$. Experimental methods for measuring $C$ are discussed.