Microscopic changes in HoNi₂B₂C due to thermal treatment and its effect on superconductivity

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Dertinger, Armin ; Dinnebier, Robert E. ; Kreyssig, A. ; Stephens, Peter W. ; Pagola, Silvina ; Loewenhaupt, M. ; van Smaalen, Sander ; Braun, Hans F.:
Microscopic changes in HoNi₂B₂C due to thermal treatment and its effect on superconductivity.
In: Physical Review B. Bd. 63 (2001) Heft 18 . - No. 184518.
ISSN 0163-1829
DOI: https://doi.org/10.1103/PhysRevB.63.184518

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Abstract

The low-temperature properties of HoNi2B2C strongly depend on its thermodynamic state established via thermal treatment. We present high resolution x-ray powder diffraction data taken on a pair of polycrystalline samples with identical chemical composition (HoNi2B2.1C) but annealed at different temperatures, namely, at 800 and at 1100 °C. Their superconducting transition temperatures differ by more than 10%. Rietveld refinement and difference Fourier analysis reveal subtle differences in the atomic parameters and in the electron density on the carbon site. Furthermore, a new atomic site can be identified for both samples, which is partially occupied with the lighter atoms boron or carbon.