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Spintronics increases the functionality of information processing while seeking to overcome some of the limitations of conventional electronics. The spin-injected field effect transistor, a lateral semiconducting channel with two ferromagnetic electrodes, lies at the foundation of spintronics research. We demonstrated a spin-injected field effect transistor in a high-mobility InAs heterostructure with empirically calibrated electrical injection and detection of ballistic spin-polarized electrons. We observed and fit to theory an oscillatory channel conductance as a function of monotonically increasing gate voltage.

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The controlled creation, manipulation and detection of spin-polarized currents by purely electrical means remains a central challenge of spintronics. Efforts to meet this challenge by exploiting the coupling of the electron orbital motion to its spin, in particular Rashba spin-orbit coupling, have so far been unsuccessful. Recently, it has been shown theoretically that the confining potential of a small current-carrying wire with high intrinsic spin-orbit coupling leads to the accumulation of opposite spins at opposite edges of the wire, though not to a spin-polarized current. Here, we present experimental evidence that a quantum point contact -- a short wire -- made from a semiconductor with high intrinsic spin-orbit coupling can generate a completely spin-polarized current when its lateral confinement is made highly asymmetric. By avoiding the use of ferromagnetic contacts or external magnetic fields, such quantum point contacts may make feasible the development of a variety of semiconductor spintronic devices.

A novel stress-induced method to grow semimetallic Bi nanowires along with an analysis of their transport properties is presented. Single crystalline Bi nanowires were found to grow on as-sputtered films after thermal annealing at 260-270 degrees C. This was facilitated by relaxation of stress between the film and the thermally oxidized Si substrate that originated from a mismatch of the thermal expansion. The diameter-tunable Bi nanowires can be produced by controlling the mean grain size of the film, which is dependent upon the thickness of the film. Four-terminal devices based on individual Bi nanowires were found to exhibit very large transverse and longitudinal ordinary magnetoresistance, indicating high-quality, single crystalline Bi nanowires. Unusual transport properties, including a mobility value of 76900 cm(2)/(V s) and a mean free path of 1.35 mum in a 120 nm Bi nanowire, were observed at room temperature.

The spin injection technique has been used to study the transport of spin polarized conduction electrons in gold films, and has resulted in the unique observation of a large "spin bottleneck" effect. Furthermore, the measured spin diffusion length is surprisingly long.PACS numbers: 72.15. Gd, 75.50.Rr The transport of spin polarized conduction electrons in metals has been a continuing topic of study in condensed matter physics. The earliest technique, conduction electron spin resonance, relied on a static magnetic field and microwave excitation to create nonequilibrium populations of electron spins in bulk metal samples [1]. In a seminal experiment [2] by Tedrow and Meservey, the quasiparticle density of states of a thin Al film was Zeeman split by a static magnetic field, and tunneling conductance measurements made with a contiguous ferromagnetic film demonstrated that electrons which tunneled from the ferromagnetic film were spin polarized. This led to the discovery that the nonequilibrium spin population created by transmission electron spin resonance could be enhanced by coating the metal samples with ferromagnetic films [3], This was followed by a demonstration of the spin injection technique [4] in which a dc current driven through a ferromagnetic film into a bulk metal sample was spin polarized; this created a population of nonequilibrium spins that diffused a distance of order 0.1 mm and was detected by another ferromagnetic film used as a spin detector. Most recently, in a related field, there have been advances in the development of a spin polarized scanning tunneling microscope [5].This Letter presents a new development, a study of spin transport and diffusion in metal films. By adapting the spin injection methodology to a novel geometry, the study of spin dynamics is extended to a new regime, and a technique that can be applied to numerous novel systems is demonstrated. Gold films were studied because there is no prior measurement of the conduction electron spin relaxation time 7*2 in gold, nor in any metal film, by electron spin resonance or other suitable technique. A spin relaxation time for electrons in polycrystalline gold films is herein deduced, but more importantly this study has discovered that the nonequilibrium spin density created in this system is much larger than has been observed in any other system, and is even larger than is predicted by theory. This unusual result will have implications for topics in such fields as magnetism, and weak localization and mesoscopic transport.The technique is presented conceptually in Fig. 1. We consider a pedagogical model of an unconventional, three terminal device, shown in cross section in Fig. 1(a). A paramagnetic metal film P is sandwiched between two ferromagnetic films, F\ and F2. Each ferromagnetic film is a single domain and is thin enough such that its axis of magnetization is constrained to lie in the plane of the film. A dc current is driven through F\ into P and returned to the current source from the bottom of P. A single voltage probe ...