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

Size dependence of nanostructures: Impact of bond order deficiency

Bone tissue is a complex biocomposite material with a variety of organic (e.g., proteins, cells) and inorganic (e.g., hydroxyapatite crystals) components hierarchically organized with nano/microscale precision. Based on the understanding of such hierarchical organization of bone tissue and its unique mechanical properties, efforts are being made to mimic these organic–inorganic hybrid biocomposites. A key factor for the successful designing of complex, hybrid biomaterials is the facilitation and control of adhesion at the interfaces, as many current synthetic biomaterials are inert, lacking interfacial bioactivity. In this regard, researchers have focused on controlling the interface by surface modifications, but the development of a simple, unified way to biofunctionalize diverse organic and inorganic materials remains a critical challenge. Here, a universal biomineralization route, called polydopamine-assisted hydroxyapatite formation (pHAF), that can be applied to virtually any type and morphology of scaffold materials is demonstrated. Inspired by the adhesion mechanism of mussels, the pHAF method can readily integrate hydroxyapatites on ceramics, noble metals, semiconductors, and synthetic polymers, irrespective of their size and morphology (e.g., porosity and shape). Surface-anchored catecholamine moieties in polydopamine enriches the interface with calcium ions, facilitating the formation of hydroxyapatite crystals that are aligned to the c-axes, parallel to the polydopamine layer as observed in natural hydroxyapatites in mineralized tissues. This universal surface biomineralization can be an innovative foundation for future tissue engineering.

Mussel-Inspired Polydopamine Coating as a Universal Route to Hydroxyapatite Crystallization

FERROMAGNETIC perovskites of the form La1–XMexMnO3–Y (where Me is Ca or Sr) have been known1 since 1950, but there has been a recent resurgence of interest following the discovery of giant magnetoresistance in this class of compounds2,3. The compounds contain both Mn3+ and Mn4+ ions; as the electronic ground state of the Mn3+ ions is degenerate, their energy is lowered by a spontaneous distortion of the surrounding lattice—the Jahn–Teller effect4. The charge carriers in these materials are strongly coupled to (and mediate the ferromagnetic interaction between) the manganese ions5, suggesting that localized lattice distortions could also play an important role in determining the electronic and magnetic properties of these compounds. Here we investigate this possibility by examining the effect on the ferromagnetic transition temperature of varying the oxygen isotope mass (replacing 16O with 18O). For La0.8Ca0.2MnO3+y, we measure an isotope shift of >20 K, significantly larger than that found for any magnetic or electronic phase transition in other oxides. In contrast, we observe no significant isotope shift for the structurally related ferromagnet SrRuO3, in which the Jahn–Teller effect is negligible. These results imply that the large isotope shift arises from coupling of the charge carriers to Jahn–Teller lattice distortions, and we suggest that such Jahn–Teller 'polarons' may also be responsible for the magnetoresistive properties of these materials.

Giant oxygen isotope shift in the magnetoresistive perovskite La1-xCaxMnO3+y

Deposition of semiconductors and metals from chemical precursors onto planar substrates is a well-developed science and technology for microelectronics. Optical fibers are an established platform for both communications technology and fundamental research in photonics. Here, we describe a hybrid technology that integrates key aspects of both engineering disciplines, demonstrating the fabrication of tubes, solid nanowires, coaxial heterojunctions, and longitudinally patterned structures composed of metals, single-crystal semiconductors, and polycrystalline elemental or compound semiconductors within microstructured silica optical fibers. Because the optical fibers are constructed and the functional materials are chemically deposited in distinct and independent steps, the full design flexibilities of both platforms can now be exploited simultaneously for fiber-integrated optoelectronic materials and devices.

https://science.sciencemag.org/content/sci/311/5767/1583.full.pdf

Microstructured Optical Fibers as High-Pressure Microfluidic Reactors

Micro-Raman and FTIR studies of synthetic and natural apatites

Expressions are derived for the effective phonon deformation potentials of polycrystalline materials, based on the properties of tensor invariants and the Voigt–Reuss–Hill averages [Proc. Phys. Soc. London Sect. A 65, 349 (1952)]. These results, and similar ones for the elastic constants, are used to determine the effect of strains on the long‐wavelength optical phonons exhibited by such materials. Application to polycrystalline Si shows that under a uniaxial or biaxial stress, the triply degenerate phonons split into singlet and doublet components that shift at different rates and appear indistinguishably in the Raman spectrum. The implications of such effects on the Raman band shape are discussed.

Polycrystalline Si under strain: Elastic and lattice‐dynamical considerations

Optical properties of nanocrystalline SnS2 thin films

IN CONVENTIONAL superconductors, the large dependence of the superconducting transition temperature (Tc) on the isotope mass (Tc∝m−α, with α≈0.5) gives strong evidence for electron pairing by a phonon-mediated mechanism. The copper oxide superconductors, on the other hand, exhibit a small oxygen isotope effect (α≈0.02; see, for example, refs 1–14), suggesting a mechanism more complex than simple phonon-mediated pairing15. To obtain further insight into this mechanism, it is important to determine the contribution from different oxygen sites in the crystal lattice to the total oxygen isotope effect. Recently, a negative isotope effect associated with oxygen atoms in the copper oxide planes of the crystal structure was reported13 for highly doped YBa2Cu3O6 + x, implying that the apical/chain oxygens make a substantial contribution to the total oxygen isotope shift. Here we investigate this effect in optimally doped YBa2Cu3O6 + x, by measuring separately the contributions to the total isotope shift of the planar and apical/chain oxygen sites. The sum of the site-selective isotope shifts equals that of the total measured shift, illustrating the self-consistency of our results. In contrast to the previous work13, we find that more than 80% of the total (positive) isotope effect is associated with the copper oxide planes.

Site-selective oxygen isotope effect in optimally doped YBa 2 Cu 3 O 6 + x

Preface. Part I: Introduction. The Discovery of HTc Superconductivity and its Decisive Circumstances J.G. Bednorz. Part II: General Problems. `S' and `d' Wave Symmetry Components in High-Temperature Cuprate Superconductors K.A. Muller, H. Keller. Theory Aspects of High-Temperature Superconductivity R. Micnas, S. Robaskiewicz. Part III: New Materials and Structures. Novel Two-Dimensional Perovskites J.G. Bednorz, et al. Mechanisms Generating Layered Cuprates and Oxycarbonates: Classification B. Raveau. Mercurocuprates: The Highest Transition-Temperature Superconductors P.P. Edwards, et al. High Pressure Crystal Growth and Properties of HgBa2Can-1CunO2n+2+delta, Sn1-xCuO2, CaCuO2 and Y2Ba4Cu6+nO14+n J. Karpinski, et al. Noncuprate Layered Perovskite Superconductor Y. Maeno, S. Ikeda. Non-Toxic HTSC Materials, Substitution in the Charge Reservoir Layer: `Cupro/Carbonate' Cuprates and Related Materials M.A. Alario-Franco, et al. Part IV: Phase Separation, Electronic Inhomogeneities, and Related Problems. 1. General. The Two-Component Paradigm for Superconductivity in the Cuprates D. Mihailovic, K.A. Muller. Two- Component High Tc Superconductivity: Charge Reservoirs, Phase Separation and Optical Excitations D. Mihailovic. 2. The La-Cuprate System. Structural Phase Transitions and Superconductivity in Lanthanum Copper Oxydes M.K. Crawford, et al. Magnetic Properties of Single-Layer Cuprates D.C. Johnston, et al. Structural Phase Transitions and Incommensurate Spin Fluctuations in the La2CuO4+y System B.O.Wells, et al. Phase Separation and Stripe-Like Modulation Observation in Cu-Doped La2CuO4+ System Z.X. Zhao, et al. 3. The Bi-Cuprate System. From a Homogeneous CuO2 Plane to a Superlattice of Quantum Stripes A. Bianconi, et al. Lattice Effect and D-Electron Delocalization Effect Around Tc in Bi-Based High-Tc Superconductors Y. Li, et al. 4. The Y-Cuprate System and Related Compounds. Lattice Instabilities, Structural Anomalies and Phase Transitions in Y1-yCayBa2Cu3Ox Phases E. Kaldis. Raman Scattering in the YBCO Compounds E. Liarokapis. Local Structure Studies of the Underdoped-Overdoped Transition in Yba2Cu3Ox. Measurement of the Yttrium X-Ray Absorption-Fine-Structure J. Roehler, et al. Neutron Spectroscopy of Rare Earths in Superconducting Materials W. Henggeler, et al. Tm NMR and Cu NQR Studies of Phase Separation in TmBaCuO Compounds M.A. Teplov, et al. Part V: Applications. Applications of High-Tc Superconductors H. Rietschel. Index.

E. Liarokapis

Papers

Micro-Raman and FTIR studies of synthetic and natural apatites

Polycrystalline Si under strain: Elastic and lattice‐dynamical considerations

Optical properties of nanocrystalline SnS2 thin films

Site-selective oxygen isotope effect in optimally doped YBa 2 Cu 3 O 6 + x

High-Tc superconductivity 1996 : ten years after the discovery