arXiv subjects

Anne Forget

Publications and source records attributed to Anne Forget.

22 records · Page 2Linked to original sources

arXiv2012

Nanoscale textured superconductivity in Ru-substituted BaFe2As2 : a challenge to a universal phase diagram for the pnictides

75As NMR experiments were performed in Ba(Fe1-xRux)2As2 for x=0 to 80%. Magnetic fractions and NMR lineshapes demonstrate that Ru substitution destroys the antiferromagnetic (AF) order inhomogeneously with a magnetic moment distributed from 0.9 to 0 uB. Superconductivity emerges at intermediate Ru doping and coexists with AF order only in the regions where moments are smaller than ~0.3uB, resulting in an original nanoscale texture. This situation contrasts with that of Co substitution, challenging the apparent universality of the phase diagram in Fe-based superconductors.

cond-mat.str-el↗

arXiv2012

BaCu3O4: High Temperature Magnetic Order in One-Dimensional S=1/2 Diamond-Chains

The magnetic properties of the alkaline earth oxocuprate BaCu3O4 are investigated. We show that the characteristic Cu3O4 layers of this material can be described with diamond chains of antiferromagnetically coupled Cu 1/2 spins with only a weak coupling between two adjacent chains. These Cu3O4 layers seem to represent a so far unique system of weakly coupled one-dimensional magnetic objects where the local AF ordering of the Cu2+ ions leads to an actual net magnetic moment of an isolated diamond chain. We demonstrate a magnetic transition at a high Néel temperature T_{N}=336 K.

cond-mat.str-el↗

arXiv2007

Room temperature coexistence of large electric polarization and magnetic order in BiFeO3 single crystals

From an experimental point of view, room temperature ferroelectricity in BiFeO3 is raising many questions. Electric measurements made a long time ago on solid-solutions of BiFeO3 with Pb(Ti,Zr)O3 indicate that a spontaneous electric polarization exists in BiFeO3 below the Curie temperature TC=1143K. Yet in most reported works, the synthesised samples are too conductive at room temperature to get a clear polarization loop in the bulk without any effects of extrinsic physical or chemical parameters. Surprisingly, up to now there has been no report of a P(E) (polarization versus electric field) loop at room temperature on single crystals of BiFeO3. We describe here our procedure to synthesize ceramics and to grow good quality sizeable single crystals by a flux method. We demonstrate that BiFeO3 is indeed ferroelectric at room-temperature through evidence by Piezoresponse Force Microscopy and P(E) loops. The polarization is found to be large, around 60 microC/cm2, a value that has only been reached in thin films. Magnetic measurements using a SQUID magnetometer and Mossbauer spectroscopy are also presented. The latter confirms the results of NMR measurements concerning the anisotropy of the hyperfine field attributed to the magnetic cycloidal structure.

cond-mat.mtrl-sci↗

arXiv2003

Phonon dispersion in 1-layer cuprate HgBa2CuO4+d

We investigate the low energy acoustical and optical modes in $\mathrm{HgBa_2CuO_{4+δ}}$ using inelastic x-ray scattering (IXS). The experimental phonon dispersion and the dynamical structure factor are compared with an atomic shell model, and the set of the atomic potentials obtained are discussed. Our results are also compared with those obtained by Raman spectroscopy and with density-of-state data measured by inelastic neutron scattering.

cond-mat.supr-con↗