We present the first spintronic semiconductor field effect transistor. The injector and collector contacts of this device were made from magnetic permalloy thin films with different coercive fields so that they could be magnetized either parallel or antiparallel to each other in different applied magnetic fields. The conducting medium was a two dimensional electron gas (2DEG) formed in an AlSb/InAs quantum well. Data from this device suggest that its resistance is controlled by two different types of spin-valve effect: the first occurring at the ferromagnet-2DEG interfaces; and the second occurring in direct propagation between contacts.PACS numbers: 71. 70E, 73.35, 75.30G, 73.20 The idea of electronic devices which exploit both the charge and spin of an electron for their operation has given rise to the new field of 'spintronics', literally spinelectronics [1,2]. The two-component nature of spintronic devices is expected to allow a simple implementation of quantum computing algorithms as well as producing spin transistors and spin based memory devices [1,2]. However, this new field has yet to have any real impact on the semiconductor microelectronics industry since no implementation of a spintronic device has appeared in the form of a semiconductor field effect transistor (FET).Spin-polarized electron transport from magnetic to non-magnetic metals has been the subject of intense investigation since the early 70's when Tedrow and Meservey [3] demonstrated the injection of a spinpolarized current from ferromagnetic nickel to superconducting aluminium. This work was subsequently extended to include spin-dependent transport between other materials. The investigation of ferromagneticferromagnetic/paramagnetic materials [4,5] resulted in the important discovery of the giant magnetoresistance effect [6,7]. Work on ferromagnetic-semiconductor systems has so far been more limited. Alvarado and Renaud [8] have demonstrated spin-polarized tunneling from a ferromagnet into a semiconductor by analyzing luminescence induced by a tunneling current between a nickel tip and a GaAs surface in a scanning tunneling microscope (STM). Similar experiments were conducted by Sueoka et al [9] and Prins et al [10].In this paper, we present results from a spintronic semiconductor FET based on the theoretical ideas of Datta and Das [11]. In their proposed FET, resistance modulation is achieved through the spin-valve effect [12] by varying the degree of spin precession which occurs in a two dimensional electron gas (2DEG) between identical ferromagnetic contacts. In our device, resistance modulation is also achieved through the spin-valve effect but by having ferromagnetic contacts with different coercivities and varying an applied magnetic field. We show that the low field magnetoresistance of the device results from two types of spin-valve effect: a ferromagnet-semiconductor contact resistance; and a direct effect between the magnetic contacts.The device consisted of a 2DEG formed in a 15nm wide InAs well between two AlSb barriers....
The magnetic Compton profiles (MCPs) measured in the [100], [110], [111] and [112] directions in single-crystal nickel with an incident photon beam of energy 224 keV are presented and discussed. The momentum resolution achieved, of 0.43 atomic units, improves on previous studies by almost a factor of two, and facilitates the interpretation of the MCPs in terms of the underlying spin-dependent momentum densities. Calculations have been performed using the linear muffin-tin orbital method, within both the local spin-density approximation (LSDA) and the generalized gradient approximation (GGA). Comparison with experiment reveals the limitations of the LSDA at low momentum, where the GGA is better able to reproduce the contribution of the s-and p-like electrons. All of the calculations overestimate the moment associated with the d-like electrons, for momenta corresponding to the first Brillouin zone. We also confirm the existence of the so-called Umklapp shoulders, which derive from the Fermi surface topology.
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