Damien Saurel

Crystal chemistry of Na insertion/deinsertion in FePO4–NaFePO4

In this paper we examine the mechanism of Na insertion and extraction in the FePO4–NaFePO4 system. Chemical preparation of the intermediate Na1−xFePO4 phase has revealed the existence of a range of stable compositions with different Na+/vacancy arrangements. The mechano-chemical aspects of the charge and discharge reactions are also discussed.

Nonlinear effects and Joule heating in I-V curves in manganites

We study the influence of the Joule effect on the nonlinear 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 diffractions. 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 is at the origin of the nonlinearity observed in the I-V curves. Consequences on other compounds with colossal magnetoresistance are also discussed.

Neutron scattering evidence for magnetic-field-driven abrupt magnetic and structural transitions in a phase-separated manganite

Substitutions at the Mn site of the charge-ordered

Magnetic field dependence of the magnetic phase separation in Pr1_xCaxMnO3 manganites studied by small-angle neutron scattering

{\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}

Stress-induced metallic behavior under magnetic field in Pr1−xCaxMnO3 (x=0.5 and 0.4) thin films (invited)

manganite is an effective way to induce abrupt jumps on the magnetic-field-driven magnetization curve. In order to get new insights into the origin of this remarkable feature, the

Small-angle neutron scattering study of the steplike magnetic transformation in Pr0.70Ca0.30MnO3

{\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{Mn}}_{0.97}{\mathrm{Ga}}_{0.03}{\mathrm{O}}_{3}

On the dynamics of transition metal migration and its impact on the performance of layered oxides for sodium-ion batteries: NaFeO2 as a case study

perovskite manganite has been studied by neutron diffraction versus temperature and at 2.5 K in an applied magnetic field up to 6 T. A weak and complex antiferromagnetic order is found for the low-temperature ground state. Magnetic transitions, associated with structural ones, are evidenced for certain strengths of magnetic field, which gives rise to the steplike behavior corresponding to the magnetization curve. Small-angle neutron scattering provides evidence for a nucleation process of micron-size ferromagnetic domains which follows the magnetization behavior.

Stress-induced metallic behavior under magnetic field in Pr

Transport properties of manganese oxides suggest that their colossal magnetoresistance (CMR) is due to percolation between ferromagnetic metallic (FM) clusters in an antiferromagnetic insulating (AFI) matrix. We have studied small-angle neutron scattering under applied magnetic field in CMR Pr1-xCaxMnO3 crystals for x around 0.33. Quantitative analysis of the small-angle magnetic neutron scattering shows that the magnetic heterogeneities take place at different scales. At the mesoscopic scale (200nm), the inhomogeneities correspond to the percolation of the conducting ferromagnetic phase into the insulating phases. It is at the origin of the colossal magnetoresistance of the compound. The other inhomogeneities are nanoscopic: inside the antiferromagnetic phase (AFI), there exist small ferromagnetic clusters. Inside the ferromagnetic phase which exists in absence of magnetic field in some compounds and is in fact insulating (FI), there also exist small non ferromagnetic objects. No evolution of this nanostructure is observed when the magnetic field is applied. The existence of such nanoscale objects is discussed in relation to the cationic disorder of these compounds.

_{1-x}

We have investigated the role of the stress-induced by the presence of the substrate in thin films of colossal magnetoresistive manganites on structural, resistive and magnetic properties. Because of the strong coupling between the small structural distortions related to the charge-ordering (CO) and the resistive properties, the presence of the substrate prevents the full developpement of the charge ordering in Pr

Ca

_{0.5}