X-ray emission spectroscopy clarifies local magnetism of iron-based superconductors

rofessor Young-June Kim (University of Toronto, Canada) and his colleagues have recently reported a Fe Kβ X-ray emission spectroscopy study on iron-based superconductors, such as PrFeAsO, Ba(Fe,Co)₂As₂, LiFeAs, Fe_1+x(Te,Se), and A₂Fe₄Se₅ (where A=K, Rb, and Cs). They found that the materials possess local magnetic moments even in their paramagnetic phases. By analyzing Fe Kβ_1,3 and Kβ' spectra using the integrated absolute difference method, the local moment size for each sample was determined. It was found that the value is independent of temperature or carrier concentration but varies significantly across different families. Specifically, all iron pnictide samples have local moments of about 1μ_B/Fe, while FeTe and K₂Fe₄Se₅ families have much larger local moments of ~2μ_B/Fe and ~3.3μ_B/Fe, respectively. Such differences point to the importance of considering the contribution of multi-orbital physics in describing magnetism of these compounds. For more information, see the paper, "Revealing the dual nature of magnetism in iron pnictides and iron chalcogenides using X-ray emission spectroscopy", H. Gretarsson et al., Phys. Rev. B84, 100509(R) (2011).