5 - Spintronic Materials, Synthesis, Processing and Applications

Abstract

Spintronics (spin electronics) refers, fundamentally, to the study and application of the extra degree of freedom of carriers (e.g., electrons), namely their spin moment for the development of multifunctional and novel devices. These devices include spin valves, magnetoresistive sensors, read heads, etc. It is expected that a merger of different areas such as electronics, photonics, and magnetics will lead to devices such as spin-FETs (field-effect transistors), spin light-emitting diodes, spin resonant tunneling devices (RTDs), optical switches operating at terahertz frequencies, and modulators. Currently, integrated circuits made of semiconductors use the charge of electrons for high-frequency information processing, whereas spin of electrons is used for storing information. All spintronic, or more specifically semiconductor spintronic, devices act according to the following simple scheme: information is stored (written) into spins as a particular spin orientation; the spins, being attached to mobile electrons, carry the information along a wire; and the information is read at a terminal. Hence, the main three requirements for a spintronic device are a source material for spin injection, a medium for transport of spin polarized electrons, and a drain or analyzer for spin detection or sensing. There are several requirements for achieving practical spintronics devices. These include the capability of transporting the carriers with high transmission efficiency within the host semiconductor or conducting oxide, the capability of detecting or collecting the spin-polarized carriers, and to be capable of controlling transport through external means such as biasing of a gate contact on a transistor structure. These aspects of spin injection, spin-dependent transport, manipulation, and detection form the basis of current research and future technology.