Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

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Sliding Friction-Physical Principles and Applications

The oxides of copper (CuxO) are fascinating materials due to their remarkable optical, electrical, thermal and magnetic properties. Nanostructuring of CuxO can further enhance the performance of this important functional material and provide it with unique properties that do not exist in its bulk form. Three distinctly different phases of CuxO, mainly CuO, Cu2O and Cu4O3, can be prepared by numerous synthesis techniques including, vapour deposition and liquid phase chemical methods. In this article, we present a review of nanostructured CuxO focusing on their material properties, methods of synthesis and an overview of various applications that have been associated with nanostructured CuxO.

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Nanostructured copper oxide semiconductors: a perspective on materials, synthesis methods and applications

Enzymes are highly efficient catalysts extensively employed in biotechnology. Among the many challenging aspects in this area, enzymes are yet difficult to obtain and purify, which makes them extremely expensive. Therefore, the industrial use of such expensive biocatalysts suffers from a critical point, which is the lack of efficient recovery processes. As a very promising strategy, superparamagnetic nanoparticles based on magnetite (Fe3O4) and maghemite (γ-Fe2O3) have been recently employed as supporting materials for enzymes, exhibiting striking characteristics, such as large surface area, mobility and high mass transference. More than that, they can be easily recovered by applying an external magnetic field. In addition to their excellent environmental compatibility, the use of such superparamagnetic nanoparticles represents an effective green chemistry approach, since it prolongs, through the successive recovery cycles, the useful lifetime of the biocatalyst. Several enzymes and biomolecules, including antibodies, albumin, α-chymotrypsin, aminopeptidase, acetylcholine esterase, amylase, amyloglucosidase, celullase, epoxide hydrolases, esterase, lipase, lysozyme, pectinases, phosphatase, pyruvate phosphate dikinase, trypsin, subtilisin, urease, chitosanase, haloalkane dehalogenase, RNA polymerase, lactate dehydrogenase, alcohol dehydrogenase, galactosidase, catalase, cholesterol oxidase, d -amino acid oxidase, cathecol dioxygenase, fructosyl amino acid oxidase, l -lactate dehydrogenase, xanthine oxidase, glucose oxidase, glucosidase, laccase, peroxidases, tyrosinase and so on, have been successfully immobilized onto magnetic nanoparticles, and the recent progress in this area is focused on this review.

Superparamagnetic nanoparticles as versatile carriers and supporting materials for enzymes

We present the composite [Y 1−x Ca x ]SrBaCu 2.80 (PO 4 ) 0.20 O y (0.10≤x≤0.40) prepared at normal temperature and pressure conditions. X-ray diffraction patterns show that samples containing Ca crystallize in a 123 tetragonal structure with small amounts of impurities. The Rietveld method was used to refine the lattice constants. Ac and dc susceptibility measurements using a SQUID show that the materials are superconductors independent of Ca content. In the normal region the measurements of χ DC show a typical Curie-Weiss law behavior.

Superconductivity and magnetism in the system [Y1−xCax]SrBaCu2.80(PO4)0.20Oy with 0.10≤x≤0.40

A complex perovskite oxide YSr2SbO6 has been synthesized by solid-state reaction. Structural ordering in this material has been studied by X-ray diffraction. The X-ray diffraction pattern reveals that YSr2SbO6 has an ordered complex cubic structure characteristic of A2BB′O6 crystalline structure with lattice constant a=8.2561 A. The chemical stability of YSr2SbO6 with YBa2Cu3O7−δ superconductors has been studied by X-ray diffraction and magnetic measurements on YSr2SbO6/YBa2Cu3O7−δ composites. Magnetic measurements show that superconducting transition temperature of pure YBa2Cu3O7−δ and YSr2SbO6/YBa2Cu3O7−δ composites is 90 K. These studies show that YSr2SbO6 could be a potential candidate as a substrate material for films of YBa2Cu3O7−δ. Furthermore, Percolation threshold VC and critical exponent t are found in the YSr2SbO6, YBa2Cu3O7−δ composite.

Structural ordering, chemical stability and percolative effect analysis in YSr2SbO6/YBa2Cu3O7-δ complex perovskite composites

A new complex cubic perovskite oxide Sr 2 HoHfO 5.5 has been prepared by solid state reaction process. X-ray diffraction studies show that Sr 2 HoHfO 5.5 has a A 2 BB ′ O 6 type complex cubic perovskite structure and presence of the significant intensities of superstructure reflections in the X-ray spectrum reveal that it is an ordered complex cubic perovskite oxide. The experimental value of the lattice parameter of Sr 2 HoHfO 5.5 , is a =8.1725 A. Based on the doubling of primitive ABO 3 cubic perovskite unit cell, (1/2) a =4.0862 A of Sr 2 HoHfO 5.5 is comparable to the lattice parameter a =3.8227 A of YBCO superconductor. Sr 2 HoHfO 5.5 has good lattice matching (lattice mismatch ∼6%) with YBCO superconductor. The dc magnetic susceptibility of Sr 2 HoHfO 5.5 , measured in the temperature range 5–300 K shows a Curie–Weiss behavior. Using a Curie–Weiss law fitting we obtain a effective magnetic moment per Ho 3+ ion in Sr 2 HoHfO 5.5 of 9.76 μ B . This value is slightly lower than the spin-only moment (10.60 μ B ) expected for an isolated Ho 3+ ion.

Synthesis and study of the structural characteristics of a new complex perovskite oxide Sr2HoHfO5.5 for its use as a substrate for YBCO superconducting films

The vortex matter in a superconducting disk with a linear configuration of metallic and superconducting defects is studied. Effects associated to the pinning (anti-pinning) force of the metallic (superconducting) defect on the vortex configuration and on the thermodynamic critical fields are analyzed in the framework of the Ginzburg Landau theory. We calculate the loop of the magnetization, vorticity and free energy curves as a function of the magnetic field for a thin disk. Due to vortex–defect attraction for a metallic defect (repulsion for a superconducting defect), the vortices always (never) are found to be sitting on the defect position.

Linear arrangement of metallic and superconducting defects in a thin superconducting sample

In this work we have studied the effect of NiS doping on the superconducting properties of the Bi-2212 (nominal composition Bi 2.1 Sr 2.1 Ca 0.8 [(CuO) 1− x (NiS) x ] 2 O 8+ δ ), superconductors. Our studies show that NiS doping stabilizes superconductivity in the system but all the NiS doped samples gave a T c lower than the superconducting transition temperature of pure Bi-2212 superconductors. It appears that NiS substitution for CuO planes and modification of the oxygen content due to S substitution on O places jointly produce strong localization of charge carriers and at the same time increase the hole concentration of the system. These combined phenomena occurring in the Bi 2.1 Sr 2.1 Ca 0.8 [(CuO) 1− x (NiS) x ] 2 O 8+ δ system are responsible for the deterioration of superconductivity of NiS doped Bi-2212 superconductors.

J. Albino Aguiar

Papers

Superconductivity and magnetism in the system [Y1−xCax]SrBaCu2.80(PO4)0.20Oy with 0.10≤x≤0.40

Structural ordering, chemical stability and percolative effect analysis in YSr2SbO6/YBa2Cu3O7-δ complex perovskite composites

Synthesis and study of the structural characteristics of a new complex perovskite oxide Sr2HoHfO5.5 for its use as a substrate for YBCO superconducting films

Linear arrangement of metallic and superconducting defects in a thin superconducting sample

Structural and magnetic properties of NiS doped Bi-2212 superconductors