arXiv subjects

Charles Simon

Publications and source records attributed to Charles Simon.

22 records · Page 2Linked to original sources

arXiv2005

Non-linear effects and Joule heating in I-V curves in manganites

We study the influence of the Joule effect on the non-linear behavior of the transport I-V curves in polycrystalline samples of the manganite Pr0.8Ca0.2MnO3 by using the crystalline unit cell parameters as an internal thermometer in X-ray and neutron diffraction. We develop a simple analytical model to estimate the temperature profile in the samples. Under the actual experimental conditions we show that the internal temperature gradient or the difference between the temperature of the sample and that of the thermal bath are at the origin of the non-linearity observed in the I-V curves. Consequences on other compounds with colossal magnetoresistance are also discussed.

cond-mat.str-el↗

arXiv2004

Anomaly in the dielectric response at the charge orbital ordering transition of crystalline Pr0.67Ca0.33MnO3

The complex impedance of a Pr0.67Ca0.33MnO3 crystal has been measured. The frequency dependence is studied for a wide range of temperatures (50K-403K) and is found to be characteristic of relaxation process with a single Debye time relaxation constant, which is interpreted as a dielectric constant of the material. A strong peak is observed in this dielectric constant (up to two millions) at the charge ordering transition suggesting an interpretation in terms of ordering of electric dipoles at TCO or in term of phase separation. Comparison with Pr0.63Ca0.37MnO3 - in which the phase separation is much smaller and the peak in the dielectric constant is absent - suggests an interpretation in term of phase separation between insulating and metallic states.

cond-mat.str-el↗

arXiv2003

The vortex depinning transition in untwinned YBaCuO using complex impedance measurements

We present surface impedance measurement of the vortex linear response in a large untwinned YBCO crystal. The depinning spectra obtained over a broad frequency range (100 Hz- 30 MHz) are those of a surface pinned vortex lattice with a free flux flow resistivity (two modes response). The critical current in the "Campbell" like regime and the flux flow resistivity in the dissipative regime are extracted. Those two parameters are affected by the first order transition, showing that this transition may be related to the electronic state of vortices.

cond-mat.supr-con↗

arXiv2003

Field dependence of the electronic phase separation in Pr0.67Ca0.33MnO3 by small angle magnetic neutron scattering

We have studied by small angle neutron scattering the evolution induced by the application of magnetic field of the coexistence of ferromagnetism (F) and antiferromagnetism (AF) in a crystal of Pr$_{0.67}$Ca$_{0.33}$MnO$_3$. The results are compared to magnetic measurements which provide the evolution of the ferromagnetic fraction. These results show that the growth of the ferromagnetic phase corresponds to an increase of the thickness of the ferromagnetic ''cabbage'' sheets.

cond-mat↗