Size Dependence of the Magnetic and Electrical Properties of the Spin-Valve Transistor

The electrical and magnetic properties of the spin-valve transistor (SVT) are investigated as a function of transistor size. A new fabrication process, designed to study the size dependence of the SVT properties, uses: silicon-on-insulator (SOI) wafers, a combination of ion beam and wet etching and a negative tone photoresist (SU8) as an insulating layer. The Si/Pt emitter and Si/Au collector Schottky barrier height do not depend on the transistor dimensions. The parasitic leakage current of the Si/Au collector is, however, proportional to its area. The relative collector current change with magnetic field is 240%, independent of size, while the transfer ratio starts to decrease for SVTs with an emitter area below 25 × 25 ¿m2. The maximum input current is found to be limited by the maximum current density allowed in the base (1.7 × 107 A/cm2), which is in agreement with the maximum current density for spin valve

Latest developments of the spin-valve transistor

The magnetic hysteresis associated with the magnetization reversal of the free layer in a spin valve is analysed. A model is proposed which assumes a single-domain behavior of the free layer, and a fixed magnetization of the pinned layer. The model is then developed in the framework of the Stoner¿Wohlfarth coherent rotation model, where geometrical solutions are obtained by the astroid method. According to the strength of the interlayer exchange coupling, the applied field direction and the anisotropy arrangement of the magnetic layers, a general classification of the hysteresis loops is proposed. Quantitative comparisons with experiments on spin valves (e.g. NiFe/Cu/NiFe/FeMn) are shown

Interface, Volume, and Thermal Attenuation of Hot-Electron Spins in Ni₈₀Fe₂₀ and Co

The relative importance of interface, volume, and thermal scattering in spin-dependent hot-electron transmission of magnetic trilayers is quantified. While interfaces produce significant attenuation (factor 2.2 per interface), the spin asymmetry is dominated by volume scattering. Extracted thermal attenuation lengths (130 Å at 300 K for Ni.......Fe...) show that thermal spin-wave scattering is stronger than hith-erto assumed. This suggests that spontaneous spin-wave emission, rather than the details of the spin-dependent band structure, may cause the strong filtering of minority hot-electron spins

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio