title: Susceptibility anisotropy in an iron arsenide superconductor revealed by x-ray diffraction in pulsed magnetic fields.
abstract: In addition to unconventional high-T(c) superconductivity, the iron arsenides exhibit strong magnetoelastic coupling and a notable electronic anisotropy within the a-b plane. We relate these properties by studying underdoped Ba(Fe(1-x)Co(x))2As2 by x-ray diffraction in pulsed magnetic fields up to 27.5 T. We exploit magnetic detwinning effects to demonstrate anisotropy in the in-plane susceptibility, which develops at the structural phase transition despite the absence of magnetic order. The degree of detwinning increases smoothly with decreasing temperature, and a single-domain condition is realized over a range of field and temperature. At low temperatures we observe an activated behavior, with a large hysteretic remnant effect. Detwinning was not observed within the superconducting phase for accessible magnetic fields.
authors.affiliation: The Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA. jpcruff@aps.anl.gov
authors.forename: J P C
authors.initials: JP
authors.lastname: Ruff
authors.forename: J-H
authors.initials: JH
authors.lastname: Chu
authors.forename: H-H
authors.initials: HH
authors.lastname: Kuo
authors.forename: R K
authors.initials: RK
authors.lastname: Das
authors.forename: H
authors.initials: H
authors.lastname: Nojiri
authors.forename: I R
authors.initials: IR
authors.lastname: Fisher
authors.forename: Z
authors.initials: Z
authors.lastname: Islam