Coexistence of Paramagnetic-Charge-Ordered and Ferromagnetic-Metallic Phases in La0.5Ca0.5MnO3 evidenced by ESR

Throughout a complete Electron Spin Resonance (ESR) and magnetization study of La0.5Ca0.5MnO3, we discuss about the nature of the complex phase-segregated state established in this compound below T~210 K. Between TN<T<TC, the ESR spectra shows two lines characteristic of two different magnetic phases. From the resonance field (Hr) derived for each line we argue that the incommensurate-charge-ordering phase (ICO) which coexists with ferromagnetic-metallic (FMM) clusters in this temperature interval, is mainly paramagnetic and not antiferromagnetic. The FMM/ICO ratio can be tuned with a relatively small field, which suggests that the internal energy associated with those phases is very similar. Below TN, there is an appreciable FM contribution to the magnetization and the ESR spectra indicates the presence of FM clusters in an antiferromagnetic matrix (canted). Our results show that ESR could be a very useful tool to investigate the nature of the phase-separated state now believed to play a fundamental role in the physics of mixed valent manganites.Comment: 6 pages, 6 figure

Single-longitudinal mode laser structure based on a very narrow filtering technique

A narrow filtering technique based on the spectral overlapping of two uniform FBGs and applied to obtain a Single Longitudinal Mode (SLM) laser is proposed and demonstrated in this work. The two FBGs are spectrally detuned to reduce their coincident reflection response narrowing the equivalent filter bandwidth. A proof-of-concept linear laser has been built and tested exhibiting SLM operation even with temperature and strain variations.The authors are grateful to the Spanish government project TEC2010-20224-C02, to the Spanish Ministry of Education and Culture, and to the grant AP2009-1403

Enhanced dimerization of TiOCl under pressure: spin-Peierls - to - Peierls transition

We report high-pressure x-ray diffraction and magnetization measurements combined with ab-initio calculations to demonstrate that the high-pressure optical and transport transitions recently reported in TiOCl, correspond in fact to an enhanced Ti3+-Ti3+ dimerization existing already at room temperature. Our results confirm the formation of a metal-metal bond between Ti3+ ions along the b-axis of TiOCl, accompanied by a strong reduction of the electronic gap. The evolution of the dimerization with pressure suggests a crossover from the spin-Peierls to a conventional Peierls situation at high pressures.Comment: 9pages, 4 figure

Coexistence of Two Rare Sarcomas: Primary Leiomyosarcoma of Bone and Epithelioid Hemangioendothelioma of the Liver

A 33-year-old woman sought medical attention for a painful swelling of the left ankle. Plain radiographs revealed an osteolytic lesion involving the left distal tibia. An excisional biopsy provided the diagnosis of leiomyosarcoma in the tibia. A staging work-up was performed and an abdominal CT showed 4 liver hypodense lesions in both lobes with peripheral contrast enhancement. A liver biopsy confirmed the diagnosis of epithelioid hemangioendothelioma of the liver. No association between these two entities has been described before. This case introduces the importance of the pathological confirmation of apparent metastatic lesions in low grade sarcomas and provides a review of the literature of both tumours

VO: A Strongly Correlated Metal Close to a Mott- Hubbard Transition

Here we present experimental and computational evidences to support that rock-salt cubic VO is a strongly correlated metal with Non-Fermi-Liquid thermodynamics and an unusually strong spin-lattice coupling. An unexpected change of sign of metallic thermopower with composition is tentatively ascribed to the presence of a pseudogap in the density of states. These properties are discussed as signatures of the proximity to a magnetic quantum phase transition. The results are summarized in a new electronic phase diagram for the 3d monoxides, which resembles that of other strongly correlated systems. The structural and electronic simplicity of 3d monoxides make them ideal candidates to progress in the understanding of highly correlated electron systems.Comment: Submitted to Phys. Rev.

Photostability of gold nanoparticles with different shapes: the role of Ag clusters

Anisotropic gold nanostructures prepared by the seed method in the presence of Ag ions have been used to study their photostability to low-power UV irradiation (254 nm) at room temperature. It has been observed that, whereas spheres are very stable to photoirradiation, rods and prisms suffer from photocorrosion and finally dissolve completely with the production of Au(III) ions. Interpretation of these differences is based on the presence of semiconductor-like Ag clusters, adsorbed onto rods and prisms, able to photocorrode the Au nanoparticles, which are absent in the case of Au spheres. We further show direct evidence of the presence of Ag clusters in Au nanorods by XANES. These results confirm a previous hypothesis ( J. Am. Chem. Soc., 2014, 136, 1182–1185) about the major influence of very stable small Ag clusters, not only on the anisotropic formation of nanostructures but also on their photostability.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Ultrahigh temperature and strain hybrid integrated sensor system based on Raman and femtosecond FBG inscription in a multimode gold-coated fiber

In this paper, a novel approach for hybrid systems combining Raman distributed sensors with fiber Bragg grating (FBG) sensors to carry out distributed and quasi-distributed temperature/strain measurements was proposed and experimentally demonstrated. Three FBGs were inscribed by the point-by-point technique in a simple setup for type I femtosecond inscription in a pure silica core multimode gold-coated fiber. Employing a single fiber, temperatures up to 600 °C and strains up to 4144 µE approximately were measured simultaneously and without interferences between both distributed and point measurements. Moreover, a new calibration technique was implemented to calibrate the distributed temperature system using the FBG measurements as reference.Spanish Government FEDER Funds (TEC2016-76021-C2-2-R)