title: Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFe2As2 family of materials.
abstract: We report a combination of Fe Kβ x-ray emission spectroscopy and density functional reduced Stoner theory calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe2(As1-xPx)2. The puzzling temperature behavior of the local moment found in rare earth-doped CaFe2As2 [H. Gretarsson et al., Phys. Rev. Lett. 110, 047003 (2013)] is also observed in CaFe2(As1-xPx)2. We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both CaFe2(As1-xPx)2 (x=0.055) and Ca0.78La0.22Fe2As2 at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the c-axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the CaFe2As2 family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides.
authors: Institute for Complex Systems (ISC-CNR), c/o Dipartimento di Fisica, Università "La Sapienza", Piazzale Aldo Moro, n. 5, 00185 Rome, Italy and Max-Planck-Institut für Festkörperforschung, Heisenbergstraβe 1, D-70569 Stuttgart, Germany.
authors: L
authors: L
authors: Ortenzi
authors: Max-Planck-Institut für Festkörperforschung, Heisenbergstraβe 1, D-70569 Stuttgart, Germany and Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada.
authors: H
authors: H
authors: Gretarsson
authors: Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
authors: S
authors: S
authors: Kasahara
authors: Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
authors: Y
authors: Y
authors: Matsuda
authors: Department of Physics, Kyoto University, Kyoto 606-8502, Japan and Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan.
authors: T
authors: T
authors: Shibauchi
authors: Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14853, USA.
authors: K D
authors: KD
authors: Finkelstein
authors: Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada.
authors: W
authors: W
authors: Wu
authors: Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada.
authors: S R
authors: SR
authors: Julian
authors: Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada.
authors: Young-June
authors: YJ
authors: Kim
authors: Code 6390, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA.
authors: I I
authors: II
authors: Mazin
authors: Institute for Theoretical and Computational Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria.
authors: L
authors: L
authors: Boeri