Raman study of element doping effects on the superconductivity of MgB2

Abstract

The influences of phonon frequency and unit cell volume on the superconductivity of element-doped MgB2 are discussed with reference to a Raman study on SiC, C, Mn, and Al−Ag-doped Mg−B materials. A phenomenon has been found in the doped samples, in that the phonon frequency changes to counteract the crystal lattice variation to keep the system stable within a Grüneisen parameter of 2.0–4.0. The chemical doping effects on phonon frequency and unit cell volume can be explained by the harmonicity-anharmonicity competition in the compounds. A decreased electronic density of states is responsible for the depression of superconductivity that is seen in doped MgB2. The possibility of a high critical temperature, Tc, in the Mg−B system exists if the material can possess both a high phonon frequency and a big unit cell volume at the same time, as indicated by the isotope effect and hydrogenation experiments.

Source-reported materials — not catalogue approval

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