Spintronics Materials with High-Spin Polarization

This chapter reviews the exploration of quaternary ferromagnetic (FM) Heusler alloys with high-spin polarization and their applications to magnetoresistive devices. Of the most successful spintronics devices are tunneling magnetoresistance (TMR) devices for read sensor applications in hard disk drives (HDDs). Due to the invention of giant magnetoresistance (GMR) in ferromagnetic/nonmagnetic multilayers by Baibich and Grünberg and the subsequent invention of spin valves, the areal density of HDDs has increased dramatically due to improvements to the sensitivity of GMR sensors. The spin polarization of materials has to be promptly measured to explore highly spin polarized materials. TMR devices are the most successful spintronics device applications that have thus far been industrially implemented. The chapter highlights that some of the newly developed quaternary Heusler alloys were found to be promising FM materials in spintronics devices such as current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) and lateral spin valve (LSV).