Spin Torque Devices

Abstract

In this chapter, spin-transfer torque (STT) effect in materials and devices specifically in spin-transfer torque magnetoresistive random access memory (STT-MRAM) has been presented. Conventional electronic devices use electric charge in contrast to spintronic devices that use spin in addition to the charge of the electron. In the STT effect spin orientation in the magnetic layer of magnetic tunnel junction (MTJ) is changed by applying spin-polarized (SP) current. STT-MRAM is a non-volatile memory device that uses MTJ to store information. Different materials and device technologies reviewed where STT is being implemented with special emphasis on MTJs with a perpendicular easy axis. In the recent decade, STT-MRAM has attracted much attention due to fascinating properties such as non-volatile, high retention properties, relatively fast write speed, and scalability in comparison to other memory devices. The previous literature inferred that CoFeB/MgO/CoFeB based MTJs are a promising material for STT-MRAM devices. Furthermore, materials for future use are also discussed. Ferromagnets (FM) based on Heusler alloys (HAs) may also be used in the future owing to their high spin polarization (SP) and high Curie temperature (Tc). In addition to STT-MRAM spin-orbit torque (SOT) MRAM is also discussed.