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arXiv · 0904.0767

Static and Dynamic Magnetism in Underdoped Superconductor BaFe$_{1.92}$Co$_{0.08}$As$_2$

A. D. Christianson·M. D. Lumsden·S. E. Nagler·G. J. MacDougall·M. A. McGuire·A. S. Sefat·R. Jin·B. C. Sales·D. Mandrus
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Abstract

We report neutron scattering measurements on single crystals of BaFe$_{1.92}$Co$_{0.08}$As$_2$. The magnetic Bragg peak intensity is reduced by 6 % upon cooling through T$_C$. The spin dynamics exhibit a gap of 8 meV with anisotropic three-dimensional (3d) interactions. Below T$_C$ additional intensity appears at an energy of $\sim$4.5(0.5) meV similar to previous observations of a spin resonance in other Fe-based superconductors. No further gapping of the spin excitations is observed below T$_C$ for energies down to 2 meV. These observations suggest the redistribution of spectral weight from the magnetic Bragg position to a spin resonance demonstrating the direct competition between static magnetic order and superconductivity.

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A. D. Christianson, M. D. Lumsden, S. E. Nagler, G. J. MacDougall, M. A. McGuire, A. S. Sefat, R. Jin, B. C. Sales, D. Mandrus. 2009-04-05. Static and Dynamic Magnetism in Underdoped Superconductor BaFe$_{1.92}$Co$_{0.08}$As$_2$. https://doi.org/10.1103/physrevlett.103.087002

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