Antiferromagnetic domains in nickel oxide by magnetic neutron laue diffraction

Two kinds of domains had been observed in antiferromagnetic nickel oxide: T-domains, associated with the four 〈111〉 propagation vectors and S-domains, associated with the three equivalent antiferromagnetic directions within a T-domain. Taking advantage of the direct interaction of neutrons with the arrangement and direction of magnetic moments, the T and S antiferromagnetic domain distributions are investigated in several single crystal samples by magnetic neutron Laue diffraction (MNLD). The T-domain behaviour when a stress is applied is qualitatively investigated. In white beam a direct topographic observation and identification of T-domains are presented. By simultaneously measuring the relative intensities of magnetic Bragg reflections from a sample with preferential domain population it is possible to confirm the direction of sublattice magnetization which had been obtained by an optical method. The S-domain distribution is studied as a function of the magnetic field on the one hand, and as a function of time on the other. This last phenomenon is very similar to the well-known magnetic after-effect which occurs in most ferromagnets. It is concluded that MNLD could be a very valuable technique to investigate many topics of magnetism.