Neutron Scattering from Magnetite below 119°K

Abstract

A neutron-scattering experiment to look for spin-wave excitation-energy changes of magnetite at the transition point 119°K showed no such change. During this work we discovered, however, that the low-temperature structure gives rise to weak extra neutron-diffraction lines that can be indexed as (h, k, l±½) in cubic indices. From the observed neutron polarization sensitivity of the intensities and the increasing structure factors with increasing sinθ/λ, we conclude that the extra reflections are not directly due to magnetic ordering (ferrimagnetic spirals or Fe2+–Fe3+ ordering on the octahedral sites). Rather they are caused by a lowering of the crystal symmetry.