A. Caneiro

Transport and magnetic properties of nanocrystalline La2/3Srl/3MnO3 powders synthesized by a nitrate–citrate gel-combustion process

Abstract We present magnetic and transport properties of nanocrystalline La 2/3 Sr l/3 MnO 3 powders prepared following a novel gel-combustion method using citric acid as the fuel. Magnetization ( M ) and magnetoresistance (MR) loops as a function of the applied magnetic field show that the coercive magnetic field H c is significantly different to the field H c * for which the resistance is maximum. A power-law dependence of the MR with magnetization, MR∝M n , with n ⩾2.5 has been observed at low fields between 5 and 200xa0K. The results are discussed in terms of spin-polarized tunneling models with a distribution of particle size in our sample.

Depression of the weak-ferromagnetism of CuO2 planes in Gd2CuO4 through Ce and Th doping

Abstract Gd 2−x Ce x CuO oxides belong to a family of recently discovered electron doped cuprate superconductors. The undoped material Gd 2 CuO 4 shows antiferromagnetic ordering of the Cu moments about room temperature. We report here ESR and static magnetization measurements made in ceramic samples which indicate a depression of the ordering temperature at a rate of 18 K/at%Ce, down to the Ce solubility limit of x∽0.16, where the material orders below 180 K. A similar rate of depression has been observed for a sample with Th substitution for Gd ions.

Energy-dispersive X-ray absorption spectroscopy at LNLS: investigation on strongly correlated metal oxides

An energy-dispersive X-ray absorption spectroscopy beamline mainly dedicated to X-ray magnetic circular dichroism (XMCD) and material science under extreme conditions has been implemented in a bending-magnet port at the Brazilian Synchrotron Light Laboratory. Here the beamline technical characteristics are described, including the most important aspects of the mechanics, optical elements and detection set-up. The beamline performance is then illustrated through two case studies on strongly correlated transition metal oxides: an XMCD insight into the modifications of the magnetic properties of Cr-doped manganites and the structural deformation in nickel perovskites under high applied pressure.

Synthesis method, control of cationic composition and superconducting behavior of Nd1.85Ce0.15Cu1±δOy

Abstract Samples of Nd 1.85 Ce 0.15 Cu 1 ± ° O y (0.99 ⩽ ± δ ⩽ 1.02) were prepared by a solid-state reaction (SSR), nitrate-decomposition method (NDM) and liquid-mix method (LMM) and characterized by XRD, SEM, EPMA, DTA and DC magnetization. The control of Cu content, substitutional impurities and Ce homogeneity depends on the synthesis method, which modifies the microstructure and the superconducting behavior of these materials. Our results show that in Nd 1.85 Ce 0.15 Cu 1 ± δ O y small variations of δ strongly affect the superconducting properties. For 1 + δ > 1.00 the Meissner fraction and the superconducting transition are substantially improved.

Stability of Jahn Teller distortion in LaMnO3 under pressure: An x-ray absorption study

The local environment of manganese atoms in

Jahn—Teller effects on the superexchange interactions in LaMnO3

mathrm{La}mathrm{Mn}{mathrm{O}}_{3}

High temperature thermodynamic properties, orthorhombic/tetragonal transition and phase stability of GdBa2Cu3Oy and related R123 compounds

under pressure up to

Mn-2p XPS spectra of differently hole-doped Mn perovskites

15.3phantom{rule{0.3em}{0ex}}mathrm{GPa}

Copper content and superconductivity of Nd1.85Ce0.15Cu1+δOy

has been studied by x-ray absorption spectroscopy. For pressures below

Phase separation region in the phase diagram of polycrystalline Pr0.65Ca0.35−xSrxMnO3

8phantom{rule{0.3em}{0ex}}mathrm{GPa}