Crystal structure of the Mg${}_{1-x}$Al${}_x$B${}_2$ superconductors near x=0.5

Abstract

Precise structural information on the Mg1-xAlxB2 superconductors in the vicinity of x 0.5 is derived from high-resolution synchrotron X-ray powder diffraction measurements. We find that a hexagonal superstructure, accompanied by doubling of the c-axis, ordering of Mg and Al in alternating layers, and a shift of the B layers towards Al by ~0.1 A, is formed. The unusually large width of the (001/2) superlattice peak implies the presence of microstrain broadening, arising from anisotropic stacking of Al and Mg layers and/or structural modulations within the ab plane. The ordered phase survives only over a limited range of compositions away from the optimum x= 0.5 doping level.

4 pages, 4 figures

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Cited by in corpus (8)

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• ${}^{11}$B and ${}^{27}$Al NMR spin-lattice relaxation and Knight shift study of Mg${}_{1-x}$Al${}_x$B${}_2$. Evidence for anisotropic Fermi surface
• Aluminium substitution induced superstructures in Mg1-xAlxB2 (x = 0.0 to 0.50): An X-ray diffraction study
• Ab initio modeling of superconducting alloys
• Is Delta_{pi}-gap-only superconductivity possible in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2} alloys?
• Enhancing long-range order in disordered two-band s-wave superconductors