Magnetism in iron-based high-temperature superconductors and its effect on lattice and superconductivity

Shortly after the discovery of iron-based high-temperature superconductors in 2008, extensive studies using neutron and x-ray scattering techniques have revealed a strong interconnection of magnetism, lattice and superconductivity. In this presentation I will give an overview of the complex interplay between these phenomena and will bring it into context with other unusual superconductors. I will illustrate the phase relations exemplarily on the family of $A$Fe$_2$As$_2$-based material ($A$ = Ba, Sr, Ca) where a stripe-like antiferromagnetic order is coupled to a lattice distortion implying a strong coupling between magnetism and structure. Partial chemical element substitution suppresses these transitions and superconductivity occurs. \\[4pt] The study was performed in collaboration with M. G. Kim$^{*}$, G. S. Tucker$^{*}$, D. K. Pratt$^{*}$, S. Nandi$^{*}$, W. Tian$^{\#}$, J. Zarestky$^{*}$, J.-W. Kim$^+$, G. E. Granroth$^{*}$, K. Marty$^{\#}$, M. D. Lumsden$^{\#}$, T. Heitmann$^{=}$, A. Thaler$^{*}$, N. Ni$^{*}$, S. L. Bud'ko$^{*}$, P. C. Canfield$^{*}$, R. M. Fernandes$^{*}$, J. Schmalian$^{*}$, R. J. McQueeney$^{*}$, and A. I. Goldman$^{*}$; $^{*}$Ames Laboratory, and Iowa State University; $^+$APS, Argonne; $^{\#}$HFIR, Oak Ridge; $^{=}$MURR, University of Missouri.