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Influence of Mg deficiency in MgB2 single crystals on crystal structure and superconducting properties by Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Batlogg, B.; Bernardini, F.; Massidda, S.; Puzniak, R. is a scholarly article available to read on EtoBox.

What is Influence of Mg deficiency in MgB2 single crystals on crystal structure and superconducting properties about?

The effects of high-temperature vacuum-annealing induced Mg deficiency in MgB2 single crystals grown under high pressure were investigated. As the annealing temperature was increased from 800 to 975 C, the average Mg content in the MgB2 crystals systematically decreased, while Tc remains essentially unchanged and the superconducting transition slightly broadens from 0.55 K to 1.3 K. The reduction of the superconducting volume fraction was noticeable already after annealing at 875 C. Samples annealed at 975 C are partially decomposed and the Mg site occupancy is decreased to 0.92 from 0.98 in as-grown crystals. Annealing at 1000 C completely destroys superconductivity. X-ray diffraction analysis revealed that the main final product of decomposition is polycrystalline MgB4 and thus the decomposition reaction of MgB2 can be described as 2MgB2(s) = MgB4(s) + Mg(g). First-principles calculations of the Mg1-x(VMg)xB2 electronic structure, within the supercell approach, show a small downshift of the Fermi level. Holes induced by the vacancies go to both sigma and pi bands. These small modifications are not expected to influence Tc, in agreement with observations. The significant reduction

Author

Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Batlogg, B.; Bernardini, F.; Massidda, S.; Puzniak, R.

Published

2010

Language

EN