Low-energy, planar magnetic defects in BaFe2As2: nanotwins, twins, antiphase and domain boundaries

الأصل · EN

In BaFe2As2, structural and magnetic planar defects begin to proliferate below the structural phase transition, affecting descriptions of magnetism and superconductivity. We study using density-functional theory the stability and magnetic properties of competing antiphase and domain boundaries, twins and isolated nanotwins (twin nuclei) - spin excitations proposed and/or observed. These nanoscale defects have very low surface energy (22-210 mJm⁻²), with twins favorable to the mesoscale. Defects exhibit smaller moments confined near their boundaries -- making a uniform-moment picture inappropriate for long-range magnetic order in real samples. Nanotwins explain features in measured pair distribution functions, so should be considered when analyzing scattering data. All these defects can be weakly mobile and/or have fluctuations that lower assessed "ordered" moments from longer spatial and/or time averaging, and should be considered directly.