On the theory of the scattering of neutrons by magnetic ions in crystals

By expanding the magnetic interaction between neutron and electron in terms of irreducible tensor operators a general expression for the coherent elastic scattering cross section is obtained. This can allow for the use of polarized beams and any scattering vector. If orbital moment is present, its effect is automatically included. This approach leads to results which are identical to those obtained by traditional methods, but the formalism is more compact and better suited to programming for computer calculations. Examples of the results from such a programme are discussed, illustrating its use as an experiment simulator. By surveying the output produced by various feasible arrangements and likely wave functions, it should be possible to discover the critical experiments which are worth undertaking.