Magnetic recording has progressed dramatically over the last 50 years, with an increase of almost eight orders of magnitude in the amount of information stored per unit area of disk space.Two key enablers of this progress have been the recording medium and the read-back head.This article reviews the current state of the art in multilayer thin-film longitudinal recording media and giant magnetoresistive (GMR) read heads, with particular emphasis on the nanostructured magnetic materials that are key to today's high-performance hard disk drives.

Organic thin-film transistors (OTFTs) are considered indispensable in applications requiring flexibility, large area, low processing temperature, and low cost. Key challenges to be addressed include developing solution-processable gate dielectric materials that form uniform films over large areas and exhibit excellent insulating properties, reducing contact resistance at interfaces between organic semiconductors and electrodes, and optimizing the patterning of organic semiconductors. High-performance pentacene-based OTFTs have been reported with polymeric gate dielectrics and indium tin oxide source/drain electrodes. Using such OTFT backplates, a 15-in. 1024 X 768 pixel full-color active-matrix liquid-crystal display (AMLCD) and a 4.5-in. 192 X64 pixel active-matrix organic light-emitting diode (AMOLED) have been fabricated.

The prediction of crystal structure is a key outstanding problem in materials science and one that is fundamental to computational materials design. We argue that by combining the predictive accuracy of quantum mechanics with data mining tools to extract knowledge from a large body of historical experimental or computational results, this problem can be successfully addressed.

The engineering of particles with customized properties optimized for dosage form manufacture (tablet, capsule, ointment, etc.) has long been a goal of the pharmaceutical industry. Particles can be designed through modification in the size, morphology, and packing arrangement of the solids. The most common approach in achieving this is through crystallization. In this bottom-up process, the two main steps, nucleation and crystal growth, both play a decisive role in shaping the quality of the final crystalline product. In this review, the role of nucleation and crystal growth in controlling particle properties is discussed, and examples are provided that demonstrate the variation in solid-state properties as a function of size, habit (morphology), and internal structure of the particles. In addition, the role of particle properties in product performance and dosage form development of pharmaceuticals is also discussed.

Ultrafast lasers have long been used to study the dynamics of fast optical, electronic, and chemical processes in materials. These tools can also be used in a variety of optical pump and probe spectroscopies to generate and detect acoustic signals with frequencies on the order of 100 GHz, and to generate and detect thermal waves with penetration depths on the scale of nanometers. The short wavelengths of these probes make them ideal for the study of the mechanical and thermal properties of thin films, their interfaces, and nanostructures. We describe the picosecond-laser acoustics technique and demonstrate how it can be used to extract the elastic constants and the adhesion of thin films and probe the normal modes of vibration of nanostructures. The thermal properties of thin films are also accessible through time-domain thermoreflectance. Since the mechanical and thermal properties can be obtained quickly on micrometer-scale regions of a sample, spatial mapping of the properties is also possible.

Over the last few years, the performance of electron microscopes has undergone a dramatic improvement, with achievable resolution having more than doubled. It is now possible to probe individual atomic sites in many materials and to determine atomic and electronic structure with single-atom sensitivity. This revolution has been enabled by the successful correction of the dominant aberrations present in electron lenses. In this review, the authors present a brief overview of these instrumental advances, emphasizing the new insights they provide to several areas of materials research.

We describe some recent advances in the methodology of using electronic structure calculations for materials design. The methods have been developed for the design of ordered metallic alloys and metal alloy catalysts, but the considerations we present are relevant for the atomic-scale computational design of other materials as well. A central problem is how to treat the huge number of compounds that can be envisioned by varying the concentrations and the number of the elements involved. We discuss various strategies for approaching this problem and show how one strategy has led to the computational discovery of a promising catalytic metal alloy surface with high reactivity and low cost.

Lipid membranes are generally thought of as flat or spherical structures, much as we would view the plasma membrane of a cell. Within the cell, however, there exists a wide variety of stacked, folded, and other forms of bent structures that support and enable such functions as photosynthesis, light-sensing, protein synthesis, molecular shuttling, chemical uptake and release, and cell division. These functions benefit from the high asymmetry of the membrane. Stacked or folded structures provide a highly concentrated and ordered assembly for facile energy and molecular transport, while bent structures facilitate budding, division, and fusion events. In this article, we survey the progress made in understanding the formation of these membrane architectures, the development of synthetic forms of stacked and folded assemblies, and the unique materials issues they present.

Although density functional theory (DFT) calculations have been widely used in many areas of the geosciences for the last 15 years, arguably the most successful application of these methods has been when they are used to understand the properties of minerals and melts in the Earth's pressures of the Earth's 6000 K and 360GPa) are so extreme that experiments under these conditions are very difficult. DFT calculations have been used to provide invaluable estimates of physical parameters that are fundamental to understanding the dynamics and evolution of the Earth. In particular, DFT calculations have helped provide estimates of the mineralogy and chemistry of the Earth's core, the high-temperature and pressure elasticity of the stable crystal phases in the mantle, the effect of defects on physical properties of mantle minerals, and, most recently, the discovery of a new phase of (Mg, Fe)SiO3 just above the core. These and other applications of DFT in the geosciences are described and their implications discussed.

Layered CoO2 materials are excellent candidates for potential thermoelectric applications. Their single crystals show good p-type thermoelectric properties at temperatures higher than 800K in air.Recently, the mechanism of thermoelectric properties was clarified through a discussion of electronic and crystallographic structure. In order to fabricate thermoelectric modules possessing good power-generation properties, thermoelectric materials and metallic electrodes must be connected with low contact resistance and high mechanical strength.It has been found that good junctions can be formed using Ag paste including p- and n-type oxide powders.The role of spin entropy contributions to thermopower will be presented, in connection with strong electron correlation and triangular lattices.

Low-defect-density polycrystalline Si on flexible substrates can be instrumental in realizing the full potential of macroelectronics. Direct deposition or solid-phase crystallization techniques are often incompatible with polymers and produce materials with high defect densities. Excimer-laser annealing is capable of producing films of reasonable quality directly on polymer and metallic substrates. Sequential lateral solidification (SLS) is an advanced pulsed-laser-crystallization technique capable of producing Si films on polymers with lower defect density than can be obtained via excimer-laser annealing. Circuits built directly on polymers using these SLS films show the highest performance reported to date.

In the development of materials for blue recording, the issues for rewritable discs relate to speed and lifetime stability. Both aspects are connected with the properties of the phase-change recording layer. Higher data rates require faster erasure (i.e., recrystallization) of previously written marks. Increasing the Sb concentration or adding specific dopants to the phase-change material appears to accelerate the crystallization rate. Faster erasure rates should, however, not promote spontaneous recrystallization at room temperature, as this would adversely affect the lifetime stability. This roomtemperature stability can be estimated from an activation energy analysis. Excellent lifetime stability proves attainable by a judicious selection of the composition of the phase-change material.

For write-once discs, the choice of the recording material is between a spin-coated dye, a phase-change layer, and an inorganic alloy. While suitable dye materials for blue wavelengths are now being developed, research into the alternative of inorganic bilayers has yielded encouraging results. Thus far, good write-once recording performance has been demonstrated with Cu/Si as the recording medium.The mechanism of mark formation in such a bilayer will be addressed. Promising results obtained with optimized Cu/Si stacks illustrate the attractiveness of this type of write-once material for blue recording.

Microfabrication techniques and scale-up by replication promise to transform classical batch-wise chemical laboratory procedures into integrated systems capable of providing new understanding and control of fundamental processes. Such integrated microchemical systems would enable rapid, continuous discovery and development of new products with the use of fewer resources and the generation of less waste. Additional opportunities exist for on-demand and on-site synthesis, with perhaps the first applications emerging in portable energy sources based on the conversion of hydrocarbons to hydrogen for miniaturized fuel cells.

Microchemical systems can be realized in a wide range of materials including stainless steel, glass, ceramics, silicon, and polymers. The high mechanical strength, excellent temperature characteristics, and good chemical compatibility of silicon combined with the existing fabrication infrastructure for microelectromechanical systems (MEMS) offer advantages in fabricating chemical microsystems that are compatible with strong solvents and operate at elevated temperatures and pressures. Furthermore, silicon-based microsensors for flow, pressure, and temperature can readily be integrated into the systems.

Microsystems for broad chemical applications should be discovery tools that can easily be applied by chemists and materials scientists while also having a convincing “scale-out” to at least small production levels. The interplay of both these capabilities is important in making microreaction technology successful. Perhaps the largest impact of microchemical systems will ultimately be the ability to explore reaction conditions and chemistry at conditions that are otherwise difficult to establish in the laboratory. Case studies are selected to illustrate microfluidic applications in which silicon adds advantages, specifically, integration of physical sensors and infrared spectroscopy, highthroughput experimentation in moisture-sensitive organic synthesis, controlled synthesis of nanoparticles (quantum dots), multiphase and heterogeneous catalytic reactions at elevated temperatures and pressures, and thermal management in the conversion of hydrocarbons to hydrogen.

The requirements for media for high-density magnetic recording are reviewed, particularly with respect to the emerging technology of perpendicular magnetic recording.It is discussed in general how suitable properties of the recording films can be achieved in practice.Several approaches to extend the thermal limit of magnetic recording technology are outlined.

The development of materials and devices at the nanoscale presents great challenges, from synthesis to assembly to characterization. Often, progress can only be made by complementing experimental work with electronic-structure modeling, harnessing the efficiency, predictive power, and atomic resolution of density functional theory to describe molecular architectures exactly at those scales (hundreds or thousands of atoms) where the most promising and undiscovered properties are to be engineered. Some of the next-generation technologies that will benefit first from first-principles simulations encompass areas as diverse as energy and information storage and retrieval, detection and sensing of biological and foreign contaminants, nanostructured catalysts, nanomechanical devices, hybrid organic-inorganic and biologically inspired materials, and novel computer technologies based on integrated optical and electronic platforms. This article reviews some of the recent successes and insights gained by electronic-structure modeling, ranging from carbon nanotubes to semiconducting nanoparticles, quantum dots, and self-assembled monolayers.

A new class of nanocomposite network materials based on carbon nanotubes or silicon nanowires for thin-film transistors promises significant improvement in the performance of large-area electronics, or macroelectronics. Evaluation of this novel materials technology requires the development of device models. A multicomponent heterogeneous stick-percolation theory is used to show that the key features of this new transistor technology are the consequences of the percolating spatial geometry of the nanosticks (nanotubes, nanorods, or nanowires) that form the channel.

This article describes the characteristics and development of materials for magnetooptical (MO) recording. Magneto-optical recording is derived from thermomagnetic recording and readout by the magneto-optical effect. Rare-earth/transition-metal alloys, mostly Tb-Fe-Co, have been used for recording materials in MO discs. MO discs were first put on the market in 1988. Magnetic-field modulation for recording was introduced in MiniDisc (MD) systems in 1992. MO discs have an advantage in durability and achievability, because recording by magnetization reversal is not accompanied by any atomic movement. Magnetically induced super-resolution (MSR), reported in 1991, enabled resolving powers that are higher than the optical limit. MO discs based on MSR were commercialized as 3.5–in. discs for data recording and as 2–in. discs for digital cameras.

As extensions of MSR, DWDD (domain-wall displacement detection) and MAMMOS (magnetic amplifying magneto-optical system) have been proposed, in which the marks are expanded during readout for a large signal. DWDD technology has been used in Hi-MDs (high-density MiniDiscs), which were commercialized in 2004 with storage capacities of 1 Gbyte per 64-mm-diameter disc.