arXiv subjects

M. Mezouar

Publications and source records attributed to M. Mezouar.

22 records · Page 2Linked to original sources

arXiv2008

Pressure-induced order-disorder phase transition in superconducting CaC6

By means of synchrotron X-ray diffraction, we studied the effect of high pressure, P, up to 13 GPa on the room temperature crystal structure of superconducting CaC6. In this P range, no change of the pristine space group symmetry, \textit{R\=3m}, is found. However, at 9 GPa, i.e. close to the critical value at which a large T_c reduction was reported recently, we observed a compressibility jump concomitant to a large broadening of Bragg peaks. The reversibility of both effects upon depressurization and symmetry arguments give evidence of an order-disorder phase transition of second order, presumably associated with the Ca sublattice, which provides a full account for the above Tc reduction.

cond-mat.supr-con↗

arXiv2007

High pressure behavior of CsC8 graphite intercalation compound

The high pressure phase diagram of CsC8 graphite intercalated compound has been investigated at ambient temperature up to 32 GPa. Combining X-ray and neutron diffraction, Raman and X- ray absorption spectroscopies, we report for the first time that CsC8, when pressurized, undergoes phase transitions around 2.0, 4.8 and 8 GPa. Possible candidate lattice structures and the transition mechanism involved are proposed. We show that the observed transitions involve the structural re- arrangement in the Cs sub-network while the distance between the graphitic layers is continuously reduced at least up to 8.9 GPa. Around 8 GPa, important modifications of signatures of the electronic structure measured by Raman and X-ray absorption spectroscopies evidence the onset of a new transition.

cond-mat.mtrl-sci↗

arXiv2006

Pressure dependence of the exchange interaction in the dimeric single-molecule magnet [Mn4O3Cl4(O2CEt)3(py)3]2 from inelastic neutron scattering

The low-lying magnetic excitations in the dimer of single-molecule magnets (Mn4)2 are studied by inelastic neutron scattering as a function of hydrostatic pressure. The anisotropy parameters D and B04, which describe each Mn4 subunit, are essentially pressure independent, while the antiferromagnetic exchange coupling J between the two Mn4 subunits strongly depends on pressure, with an increase of 42% at 17 kbar. Additional pressure dependent powder X-ray measurements allow a structural interpretation of the findings.

cond-mat.str-el↗

arXiv2001

Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry

We report measurements on MgB2 up to ~40GPa. 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 2D 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.

cond-mat.supr-con↗