Absence of a structural transition up to 40 GPa in <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="normal">MgB</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> 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 ${MgB}_{2}$ 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, and R. J. Cava

Phys. Rev. B 64, 172502 – Published 1 October 2001

Abstract

We report measurements on ${MgB}_{2}$ up to $\sim 40 GPa .$ 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 ${AlB}_{2} .$ 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 $p_{xy}$ 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.

Received 4 May 2001

DOI:https://doi.org/10.1103/PhysRevB.64.172502

Authors & Affiliations

P. Bordet

Laboratoire de Cristallographie, CNRS, B.P. 166, 38042 Grenoble Cedex 9, France

M. Mezouar

European Synchroton Radiation Facility, B.P. 220, 38043 Grenoble Cedex, France

M. Núñez-Regueiro^* and M. Monteverde^†

Centre de Recherches sur les Très Basses Températures, CNRS, B.P. 166, 38042 Grenoble Cedex 9, France

M. D. Núñez-Regueiro

Grenoble High Field Magnetic Laboratory, MPI-FKF and CNRS, B.P. 166, 38042 Grenoble Cedex 9, France

N. Rogado, K. A. Regan, M. A. Hayward, T. He, S. M. Loureiro, and R. J. Cava

Department of Chemistry and Materials Institute, Princeton University, Princeton, New Jersey 08544

^*Corresponding author. Electronic address: nunez@polycnrs-gre.fr
^†Also at Laboratorio de Bajas Temperaturas, Departamento de Física-FCEyN UBA, Ciudad Universitaria Pab. I, 1428 Buenos Aires, Argentina.

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Vol. 64, Iss. 17 — 1 November 2001

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