By introducing spin degrees of freedom in semiconductor materials and devices, we can create new functionalities in semiconductor electronics. This research field called “semiconductor spintronics” is now a major trend worldwide. In this article, we review the development of ferromagnetic semiconductors and other semiconductor-based materials with magnetic or spin-related properties, spin injection/detection, spin control in semiconductors, and device applications. Future issues and prospects are also described.

We discuss, from the microscopic view point, the dynamics of magnetic moments when an electrical current exists in magnetic materials. The divergence term −∇·J_i^S of spin current J_i^S is added to the Landau-Lifshitz-Gilbert equation. By adding this term, the magnetic moments are forced to rotate so that the total angular momentum is conserved. We further consider the microscopic origin of the Gilbert damping coefficient based on the recently developed theory.

X-ray reflectivity is a powerful method for the nondestructive analysis of structures in the depth direction of thin films and layered materials. When monochromatic X-ray photons impinge on a sample surface at the grazing incidence, some interference fringes are observed in the reflectivity curve, which is obtained as a function of the glancing angle. By whole-pattern fitting using the theoretical reflectivity and/or by Fourier analysis, one can determine the density and thickness of each layer, as well as the roughness of the surface and each interface. The technique is superior in its power of detection of very slight changes even at the atomic-layer level. The data do not depend on the crystal structure, and it is possible to apply the method to any thin film, as long as the surface and interfaces are flat and smooth. This article describes how the X-ray reflectivity technique can contribute to research and development.

Magnetoresistive memory based on magnetic tunnel junctions (MTJs) has attracted much attention. Previously, the use of this type of memory was limited due to the small magnetoresistance and large write current. However, the MTJ with a crystalline MgO tunnel barrier exhibiting very large magnetoresistance combined with a low power writing scheme based on spin-torque-induced magnetization reversal has enabled us to develop high-density nonvolatile-memory devices. In this article, we describe the development of MgO-based MTJs, the physics of spin-torque-induced magnetization reversal, and the progress of device application.

The article describes spin-functional MOSFETs and their integrated electronics applications. The current and future status of spin-MOSFET and pseudo-spin-MOSFET technologies, which can merge MOSFETs with the functions of magneto-resistive devices at device and circuit levels, respectively, are briefly reviewed. Furthermore, a power-gating processor based on nonvolatile logic, which is expected to be the most important application of spin-functional MOSFETs, is also addressed.

We present the design issues of high quality, high-power pico-second phase-conjugate lasers based on a side-pumped Nd : YVO_i bounce amplifier in combination with a photorefractive phase conjugate mirror. Average power of 26W was achieved at a pump power of 74W. The corresponding optical efficiency of 35% was obtained. We also investigated the further power scaling of the system by utilizing a cascaded booster amplifier. The system was scaled up to >75W.

We demonstrate the manipulation of nuclear spin coherence in a GaAs/AlGaAs quantum well by optically detected nuclear magnetic resonance (NMR). The phase shift of the Larmor precession of photoexcited electron spins is detected to read out the hyperfine-coupled nuclear spin polarization. Multipulse NMR sequences are generated to control the population and examine the phase coherence in quadrupolar-split spin-3/2 ⁷⁵ As nuclei.

Molecular spintronics has attracted attention in the last several years. However, there have been serious problems in this field, such as low reliability and reproducibility. In this manuscript, our approaches to solving these problems and constructing a firm basis for molecular spintronics are introduced, and in addition, our recent successes in observing spin-dependent transport via molecules and detecting spin current (not spin-polarized electric current) at room temperature are described.

For DNA chips used as a tool for analyzing genetic information, higher sensitivity and accuracy are required. The method of immobilizing probe DNA on a solid substrate is an important point in the creation of a higher-performance DNA chip. Here we introduce a novel method of DNA detection, based on the double-strand formation of DNA (hybridization) by the fabrication of a DNA self-assembled monolayer on a solid substrate. High throughput, nonlabeled and highly sensitive DNA detection is expected to be achieved by this method.

Multitemporal multispectral images of urban areas were obtained from an aircraft over a wide area, and their features and the effectiveness of this method are discussed. Spherical thermal images, in which the thermal radiation of urban living areas was measured, are presented. These images are used to analyze urban environmental problems such as the heat-island phenomenon and heat stroke. In addition, environment prediction and evaluation technology utilizing remote sensing, GIS (CAD) and a numerical thermal simulation developed by us are also introduced.