Polarized neutron scattering in magnets

General principles of polarized-neutron magnetic scattering are presented and their applications are considered. It is shown that this technique is especially useful if the system as a whole contains an axial vector interaction. The examples of the magnetic field, Dzyaloshinskii – Moriya interaction, and elastic torsion are considered. In all these cases, polarized neutron scattering provides information unavailable with other experimental methods. The theory is illustrated by pertinent experimental results, notably the confirmation of the Polyakov – Kadanoff – Wilson algebra for critical three-spin fluctuations in iron; the first determination of chiral critical exponents in the triangular-lattice antiferromagnets; and the determination of noncollinear magnetic structure for a number of complex antiferromagnets.