"Susceptibility Anisotropy in an Iron Arsenide Superconductor Revealed by X-Ray Diffraction in Pulsed Magnetic Fields"

J. P. C. Ruff: J.-H. Chu, H.-H. Kuo, R. K. Das, H. Nojiri, I. R. Fisher, and Z. Islam ; Phys. Rev. Lett. , 07/11/12.

Additional Authors: J.-H. Chu, H.-H. Kuo, R. K. Das, H. Nojiri, I. R. Fisher, and Z. Islam

Abstract:

In addition to unconventional high-Tc 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(Fe1-xCox)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.