Giant enhancement of spin accumulation and long-distance spin precession in metallic lateral spin valves

The nonlocal spin injection in lateral spin valves is highly expected to be an effective method to generate a pure spin current for potential spintronic application. However, the spin valve voltage, which decides the magnitude of the spin current flowing into an additional ferromagnetic wire, is typically of the order of 1 {\mu}V. Here we show that lateral spin valves with low resistive NiFe/MgO/Ag junctions enable the efficient spin injection with high applied current density, which leads to the spin valve voltage increased hundredfold. Hanle effect measurements demonstrate a long-distance collective 2-pi spin precession along a 6 {\mu}m long Ag wire. These results suggest a route to faster and manipulable spin transport for the development of pure spin current based memory, logic and sensing devices.Comment: 23 pages, 4 figure

Noise properties of the spin-valve transistor

Noise measurements have been performed on a spin-valve transistor. This transistor consists of a Pt/NiFe/Au/Co/Au multilayer sandwiched between two semiconductors. For comparison, we also studied metal base transistors with a Pt/Au or Pt/NiFe/Au base. All samples show full shot noise in the collector current. The inclusion of a spin-valve in the base layer decreases the absolute value of the collector current and with it the noise level but it does not change the nature of the noise in this device. Similarly, the collector current, and therefore, the noise changes as a function of magnetic field for the spin-valve transistor, but no additional noise of magnetic origin is observe

Electrical creation of spin polarization in silicon at room temperature

The control and manipulation of the electron spin in semiconductors is central to spintronics1,2, which aims to represent digital information using spin orientation rather than electron charge. Such spin-based technologies may have a profound impact on nanoelectronics, data storage, and logic and computer architectures.\ud Recently it has become possible to induce and detect spin\ud polarization in otherwise non-magnetic semiconductors (gallium arsenide and silicon) using all-electrical structures3–9, but so far only at temperatures below 150K and in n-type materials, which limits further development. Here we demonstrate room-temperature electrical\ud injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect and the electrical detection of the induced spin accumulation.\ud A spin splitting as large as 2.9meV is created in n-type\ud silicon, corresponding to an electron spin polarization of 4.6%. The extracted spin lifetime is greater than 140 ps for conduction electrons in heavily doped n-type silicon at 300K and greater than 270 ps for holes in heavily doped p-type silicon at the same temperature.\ud The spin diffusion length is greater than 230nmfor electrons\ud and 310nm for holes in the corresponding materials. These results open the way to the implementation of spin functionality in complementary silicon devices and electronic circuits operating at ambient temperature, and to the exploration of their prospects and the fundamental rules that govern their behaviour.\u

Cross-sectional imaging of spin injection into a semiconductor

Recent discoveries of phenomena that relate electronic transport in solids to the spin angular momentum of the electrons are the fundamentals of spin electronics (spintronics). The first proposed conceptual spintronic device, the spin field-effect transistor—which has not yet been successfully implemented—requires the creation and detection of spin-polarized currents in a semiconductor. Whereas electrical spin injection from a ferromagnetic metal into GaAs has been achieved recently, the detection techniques used up to now have drawbacks like the requirement of large magnetic fields or limited information about the spin polarization in the semiconductor. Here we introduce a method that, by observation across a cleaved edge, enables us to directly visualize fully remanent electrical spin injection into bulk GaAs from a ferromagnetic contact, to image the spin-density distribution in the semiconductor in a cross-sectional view and to separate the effects of spin diffusion and electron drift