Absence of a structural transition up to 40 GPa in MgB2 and the relevance of magnesium nonstoichiometry

P. Bordet; M. Mezouar; M. Núñez-Regueiro; M. Monteverde; M. D. Núñez-Regueiro; N. Rogado; K. A. Regan; M. A. Hayward; T. He; S. M. Loureiro; R. J. Cava

doi:10.1103/PhysRevB.64.172502

Absence of a structural transition up to 40 GPa in MgB2 and the relevance of magnesium nonstoichiometry

P. Bordet, M. Mezouar, M. Núñez-Regueiro, M. Monteverde, M. D. Núñez-Regueiro, N. Rogado, K. A. Regan, M. A. Hayward, T. He, S. M. Loureiro, R. J. Cava

DOI 10.1103/PhysRevB.64.172502 · Physical Review B

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Abstract

We report measurements on MgB2 up to ∼40 GPa. Increasing pressure yields a monotonous decrease of the lattice parameters and of the c/a ratio, but no structural transition down to parameters smaller than those of AlB2. The transition superconducting temperature also decreases with temperature in a sample-dependent way. The results are explained by an increase of the filling of the two-dimensional pxy bands with pressure, the Mg stoichiometry determining the starting position of the Fermi level. Our measurements indicate that these hole bands are the relevant ones for superconductivity.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	Pressure not reported	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	39 GPa	unknown