An Enhanced Methodology for Antiferromagnetic Structure and Form-factor Determinations

Abstract

It seems that it might be due to a combination of practical and historical circumstances that the unpolarised neutron diffraction method, applied usually to powder samples, still dominates structure determinations of antiferromagnets. Polarised-beam methods are used for ferromagnets. There is also a more advanced polarised-neutron single-crystal method for antiferromagnets, which is at last beginning to emerge, and this paper outlines the conceptual changes that are involved in adapting to this little-known revision of methodology, for multidomain antiferromagnetic structures. Further analyses are presented of initial UND-FFI-NPA_(A) results, for a tP3z antiferromagnet t ₁, AuMn for example, and the discussion is extended to the possibilities for further study, such as with a different UND-FFI-NPA_(D) experimental arrangement. By introducing additional techniques to determine the moment directions in individual coherent domains, the studies can proceed to more rigorous and detailed investigations of the form-factors in antiferromagnets of various symmetries. Some appropriate form-factor expressions are presented.

Key Words:

• Antiferromagnetic configuration
• antiferromagnetic domains
• form-factors
• magnetic structure
• neutron diffraction
• neutron polarisation analysis