Neutron magnetic scattering in structurally-distorted crystals

Neutron diffraction on a magnetic structure in a crystal having a structural phase transition of a distortion type is considered. It is assumed that distortion shifts of atoms are described by the star of the wave vector of a general type. It is shown that in coherent scattering satellites of different orders caused by magnetic scattering which intensities are proportional to some degree of the atom shift amplitudes of the magnetic atoms from their positions in the initial crystal phase appear round every magnetic reflex. A formula for the satellite intensities is deduced. The theory is illustrated for BaMnF4 crystals and a nickel-zinc spinel, where observed are distortion phase transitions into incommensurable structures at nitrogen temperatures with subsequent magnetic ordering in the helium temperature range