Direct imaging of the structural domains in the iron pnictides AFe(2)As(2) (A=Ca,Sr,Ba)

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Tanatar, M. A.
Kreyssig, A.
Nandi, S.
Ni, Ni
Bud'ko, Sergey L.
Prozorov, R.
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American Physical Society
Canfield, Paul
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Goldman, Alan
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Physics and Astronomy
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Ames National Laboratory

Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.

For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.

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The parent compounds of recently discovered iron-arsenide superconductors, AFe(2)As(2) with alkaline earth A=Ca,Sr,Ba, undergo simultaneous structural and magnetic phase transitions at a temperature T-SM. Using a combination of polarized light microscopy and spatially resolved high-energy synchrotron x-ray diffraction we show that the orthorhombic distortion leads to the formation of 45 degrees-type structural domains in all parent compounds. Domains penetrate through the sample thickness in the c direction and are not affected by crystal imperfections such as growth terraces. The domains form regular stripe patterns in the plane with a characteristic dimension of 10-50 mu m. The direction of the stripes is fixed with respect to the tetragonal (100) and (010) directions but can change by 90 degrees on thermal cycling through the transition. This domain pattern may have profound implications for intrinsic disorder and anisotropy of iron arsenides.
This article is published as Tanatar, M. A., A. Kreyssig, S. Nandi, N. Ni, S. L. Bud’Ko, P. C. Canfield, A. I. Goldman, and R. Prozorov. "Direct imaging of the structural domains in the iron pnictides A Fe 2 As 2 (A= Ca, Sr, Ba)." Physical Review B 79, no. 18 (2009): 180508. DOI: 10.1103/PhysRevB.79.180508. Copyright 2009 American Physical Society. Posted with permission.