Local Lattice Dynamics in the Mg0.5Al0.5B2 Superconductor |
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| Authors: | G Campi T Proffen X Qiu E S Bozin S J L Billinge S Agrestini N L Saini A Bianconi |
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| Affiliation: | (1) Istituto di Cristallografia, CNR, Via Salaria Km 29,300, 00016 Monterotondo Rome, Italy;(2) Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;(3) Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA;(4) Dipartimento di Fisica, Universita di Roma La Sapienza, P. le Aldo Moro 2, 00185 Rome, Italy |
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| Abstract: | We have studied temperature evolution of the local as well as the average crystal structure of MgB2 and Mg0.5Al0.5B2 using real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction in a wide
temperature range of T=10–600 K. The mean square relative displacements (MSRD) of atomic B–B, B–Mg (B–Al) pairs are compared with mean-square displacements
(MSD) to calculate atomic correlations. In spite of the enhanced atomic disorder in Mg0.5Al0.5B2, where the boron–boron, and boron–magnesium pair motions are found to be small, we find that the same atomic correlations
in MgB2 assume even slightly lower values and remain nearly constant in a wide temperature range of 0–600 K. This anomalous behavior
and its physical interpretation provoke new questions on our understanding to the local lattice dynamics in this material. |
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| Keywords: | MgB2 Neutron diffraction |
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