다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

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Spintronics: Fundamentals and applications

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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

The field of self-assembled monolayers (SAMs) has witnessed tremendous growth in synthetic sophistication and depth of characterization over the past 15 years.1 However, it is interesting to comment on the modest beginning and on important milestones. The field really began much earlier than is now recognized. In 1946 Zisman published the preparation of a monomolecular layer by adsorption (self-assembly) of a surfactant onto a clean metal surface.2 At that time, the potential of self-assembly was not recognized, and this publication initiated only a limited level of interest. Early work initiated in Kuhn’s laboratory at Gottingen, applying many years of experience in using chlorosilane derivative to hydrophobize glass, was followed by the more recent discovery, when Nuzzo and Allara showed that SAMs of alkanethiolates on gold can be prepared by adsorption of di-n-alkyl disulfides from dilute solutions.3 Getting away from the moisture-sensitive alkyl trichlorosilanes, as well as working with crystalline gold surfaces, were two important reasons for the success of these SAMs. Many self-assembly systems have since been investigated, but monolayers of alkanethiolates on gold are probably the most studied SAMs to date. The formation of monolayers by self-assembly of surfactant molecules at surfaces is one example of the general phenomena of self-assembly. In nature, self-assembly results in supermolecular hierarchical organizations of interlocking components that provides very complex systems.4 SAMs offer unique opportunities to increase fundamental understanding of self-organization, structure-property relationships, and interfacial phenomena. The ability to tailor both head and tail groups of the constituent molecules makes SAMs excellent systems for a more fundamental understanding of phenomena affected by competing intermolecular, molecular-substrates and molecule-solvent interactions like ordering and growth, wetting, adhesion, lubrication, and corrosion. That SAMs are well-defined and accessible makes them good model systems for studies of physical chemistry and statistical physics in two dimensions, and the crossover to three dimensions. SAMs provide the needed design flexibility, both at the individual molecular and at the material levels, and offer a vehicle for investigation of specific interactions at interfaces, and of the effect of increasing molecular complexity on the structure and stability of two-dimensional assemblies. These studies may eventually produce the design capabilities needed for assemblies of three-dimensional structures.5 However, this will require studies of more complex systems and the combination of what has been learned from SAMs with macromolecular science. The exponential growth in SAM research is a demonstration of the changes chemistry as a disciAbraham Ulman was born in Haifa, Israel, in 1946. He studied chemistry in the Bar-Ilan University in Ramat-Gan, Israel, and received his B.Sc. in 1969. He received his M.Sc. in phosphorus chemistry from Bar-Ilan University in 1971. After a brief period in industry, he moved to the Weizmann Institute in Rehovot, Israel, and received his Ph.D. in 1978 for work on heterosubstituted porphyrins. He then spent two years at Northwestern University in Evanston, IL, where his main interest was onedimensional organic conductors. In 1985 he joined the Corporate Research Laboratories of Eastman Kodak Company, in Rochester, NY, where his research interests were molecular design of materials for nonlinear optics and self-assembled monolayers. In 1994 he moved to Polytechnic University where he is the Alstadt-Lord-Mark Professor of Chemistry. His interests encompass self-assembled monolayers, surface engineering, polymers at interface, and surfaces phenomena. 1533 Chem. Rev. 1996, 96, 1533−1554

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Formation and Structure of Self-Assembled Monolayers.

The surface science of titanium dioxide

In situ FTIR study of the adsorption geometry of bisulfate accepted ions on a platinum electrode

An antiferromagnetically exchange-coupled structure for use in various types of magnetic devices, such as magnetic tunnel junctions and spin-valve giant magnetoresistance recording heads, includes an antiferromagnetic layer formed of an alloy of osmium and manganese, wherein the osmium is present in the range of approximately 10 to 30 atomic %. The antiferromagnetic layer is deposited on a non-reactive underlayer, preferably one formed of a noble metal, such as platinum, palladium or alloys thereof. The antiferromagnetic material provides a strong exchange biasing for the ferromagnetic layer that is deposited on the antiferromagnetic layer. Iridium may be added to the osmium-manganese alloy, wherein the total of osmium and iridium is in the range of the approximately 10 to 30 atomic %, to increase the blocking temperature of the antiferromagnetic material. A template layer of permalloy (nickel-iron alloy) may be formed between the underlayer and the antiferromagnetic layer to improve the growth of the osmium-manganese alloy. The resulting antiferromagnetically exchange-coupled structure exhibits very high thermal stability, i.e., the magnetoresistance of magnetic tunnel junction devices is retained even during relatively high annealing process temperatures. This allows magnetic tunnel junction devices using the structure to be used as memory cells in magnetic random access memory arrays that are formed on substrates with electronic circuitry formed by conventional high-temperature CMOS processes and which require high temperature anneals of the completed memory chips.

Antiferromagnetically exchange-coupled structure for magnetic tunnel junction device

Surface extended x-ray absorption fine structure of underpotentially deposited silver on gold(111) electrodes

For spintronic applications, such as magnetic memory and logic, magnetic thin films with high perpendicular magnetic anisotropy and spin polarization are needed. An attractive candidate material is the Heusler compound Mn3-xGa (x varying from 0 to 2). We show that there is a correlation between the degree of crystallization of thin films of Mn3-xGa (x ∼ 0.9) and the magnitude of the perpendicular magnetic anisotropy. Moreover, we find that the crystallization temperature window varies with the seed layer on which the Mn3-xGa films are deposited. Seed layers of Pt, Cr, Ru, Mo and SrTiO3 were considered and the largest crystallization window was found for Pt(100) layers.

Strong dependence of the tetragonal Mn2.1Ga thin film crystallization temperature window on seed layer

Heusler alloys are a large family of compounds with complex and tunable magnetic properties, intimately connected to the atomic scale ordering of their constituent elements. We show that using a chemical templating technique of atomically ordered X′Z′ (X′ = Co; Z′ = Al, Ga, Ge, Sn) underlayers, we can achieve near bulk-like magnetic properties in tetragonally distorted Heusler films, even at room temperature. Excellent perpendicular magnetic anisotropy is found in ferrimagnetic X3Z (X = Mn; Z = Ge, Sn, Sb) films, just 1 or 2 unit-cells thick. Racetracks formed from these films sustain current-induced domain wall motion with velocities of more than 120 m s−1, at current densities up to six times lower than conventional ferromagnetic materials. We find evidence for a significant bulk chiral Dzyaloshinskii–Moriya exchange interaction, whose field strength can be systematically tuned by an order of magnitude. Our work is an important step towards practical applications of Heusler compounds for spintronic technologies. Heusler compounds are of great interest for spintronic applications. Here the authors report current driven domain wall motion in unit cell thick perpendicularly magnetized Heusler films with low current densities and show the velocity is dominated by the bulk chiral Dzyaloshinskii–Moriya exchange interaction.

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Mahesh G. Samant

Papers

In situ FTIR study of the adsorption geometry of bisulfate accepted ions on a platinum electrode

Antiferromagnetically exchange-coupled structure for magnetic tunnel junction device

Surface extended x-ray absorption fine structure of underpotentially deposited silver on gold(111) electrodes

Strong dependence of the tetragonal Mn2.1Ga thin film crystallization temperature window on seed layer

Chiral domain wall motion in unit-cell thick perpendicularly magnetized Heusler films prepared by chemical templating.