Shell-driven magnetic stability in core-shell nanoparticles

The magnetic properties of ferromagnetic-antiferromagnetic Co-CoO core-shell nanoparticles are investigated as a function of the in-plane coverage density from 3.5% to 15%. The superparamagnetic blocking temperature, the coercivity, and the bias field radically increase with increasing coverage. This behavior cannot be attributed to the overall interactions between cores. Rather, it can be semiquantitatively understood by assuming that the shells of isolated core-shell nanoparticles have strongly degraded magnetic properties, which are rapidly recovered as nanoparticles come into contact

Magnetization of nanoparticle systems in a rotating magnetic field

The investigation of a sizable thermal enhancement of magnetization is put forward for uniaxial ferromagnetic nanoparticles that are placed in a rotating magnetic field. We elucidate the nature of this phenomenon and evaluate the resonant frequency dependence of the induced magnetization. Moreover, we reveal the role of magnetic dipolar interactions, point out potential applications and reason the feasibility of an experimental observation of this effect.Comment: 10 pages, 2 figure

Ferromagnetic tendency at the surface of CE charge-ordered manganites

Most previous investigations have shown that the surface of a ferromagnetic material may have antiferromagnetic tendencies. However, experimentally the opposite effect has been recently observed: ferromagnetism appears in some nano-sized manganites with a composition such that the antiferromagnetic charge-ordered CE state is observed in the bulk. A possible origin is the development of ferromagnetic correlations at the surface of these small systems. To clarify these puzzling experimental observations, we have studied the two-orbital double-exchange model near half-doping n=0.5, using open boundary conditions to simulate the surface of either bulk or nano-sized manganites. Considering the enhancement of surface charge density due to a possible AO termination (A = trivalent/divalent ion composite, O = oxygen), an unexpected surface phase-separated state emerges when the model is studied using Monte Carlo techniques on small clusters. This tendency suppresses the CE charge ordering and produces a weak ferromagnetic signal that could explain the experimental observations.Comment: 8 pages, 5 figure

Direct measurements of magnetostrictive process in amorphous wires using scanning tunneling microscopy

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.We demonstrate a versatile capability to measure directly the magnetostrictive properties through the magnetization process on a nanometric scale using a modified scanning tunneling microscope. Single 10 mm long, 125 μm diam amorphouswires of both positive and negative magnetostriction have been studied and the data are compared with the hysteretic loops determined by both ac and SQUID magnetic measurements. This improved technique promises interesting possibilities, from both fundamental and applications points of view, in a number of scientific disciplines especially of interest in life and environmental sciences

Biochemical data from the characterization of a new pathogenic mutation of human pyridoxine-5'-phosphate oxidase (PNPO)

PNPO deficiency is responsible of severe neonatal encephalopathy, responsive to pyridoxal-5’-phosphate (PLP) or pyridoxine. Recent studies widened the phenotype of this condition and detected new genetic variants on PNPO gene, whose pathogenetic role and clinical expression remain to be established. One of these mutations, Arg116Gln, is of particular interest because of its later onset of symptoms (beyond the first months of life) and its peculiar epileptic manifestations in patients. This protein variant was expressed as recombinant protein in E coli, purified to homogeneity, and characterized with respect to structural and kinetic properties, stability, binding constants of cofactor flavin mononucleotide (FMN) and product (PLP) in order to define the molecular and structural bases of its pathogenicity. For interpretation and discussion of reported data, together with the description of clinical studies, refer to the article [7][1] (doi: 10.1016/j.ymgme.2017.08.003)

Thickness dependence of the exchange bias in epitaxial manganite bilayers

Exchange bias has been studied in a series of La2/3Ca1/3MnO3 / La1/3Ca2/3MnO3 bilayers grown on (001) SrTiO3 substrates by ozone-assisted molecular beam epitaxy. The high crystalline quality of the samples and interfaces has been verified using high-resolution X-ray diffractometry and Z-contrast scanning transmission electron microscopy with electron energy loss spectroscopy. The dependence of exchange bias on the thickness of the antiferromagnetic layer has been investigated. A critical value for the onset of the hysteresis loop shift has been determined. An antiferromagnetic anisotropy constant has been obtained by fitting the results to the generalized Meiklejohn-Bean model.Comment: 7 pages. 8 figure

Pseudo Spin Valves Using a (112)-textured DO_22 MnGa Fixed Layer

We demonstrate pseudo spin valves with a (112)-textured DO_22 MnGa (MnGa) tilted magnetization fixed layer and an in-plane CoFe free layer. Single D0_22 MnGa films exhibit a small magnetoresistance (MR) typically observed in metals. In MnGa/Cu/ CoFe spin valves a transition from a negative (-0.08%) to positive (3.88%) MR is realized by introducing a thin spin polarizing CoFe insertion layer at the MnGa/Cu interface and tailoring the MnGa thickness. Finally, the exchange coupling between the MnGa and CoFe insertion layer is studied using a first-order reversal curve (FORC) technique.Comment: 5 pages, 4 figures, submitted to IEEE Magnetics Letter

Estudio del manejo de serpientes venenosas y actuación en caso de mordedura

La tenencia de serpientes venenosas, ya sea como mascotas o como miembros de exposiciones o de parques zoológicos, requiere de las instalaciones y de la infraestructura necesarias para garantizar la seguridad de los propietarios, y del conocimiento de su manejo. Los dispositivos utilizados tienen diversos fines: protección personal (gafas, guantes, polainas, botas), sujeción (ganchos, tubos de contención, bolsas de transporte) o alimentación (pinzas, abrebocas, sondas). En caso de mordedura, se debe recurrir a asistencia hospitalaria para que se proceda a la administración del suero antiofídico específico lo antes posible. Como primeros auxilios se debe mantener a la víctima tranquila e inmóvil, limpiar la mordedura y aplicar una bomba de succión de veneno.When venomous snakes are keep in captivity, as a pet or spice as a part of collections from zoo, some infrastructure and facilities for ensuring the people safety must be available and the staff must know how to use them. Many devices for the snakes handling have been marketed: personal protection equipment (glasses, gloves, shoes, gaiter), snake fastening devices (hooks, restlessness tubes, transport bags) or feeding gadgets (tweezers, mouth openers, feeding tubes). When somebody is bitten, hospital emergency service must be requested as soon as possible and so the specific antivenom serum will be administered. The first aid would consist on keeping the bitten individual at ease and at rest, cleaning the bite injury and using a venom suction pump