Fundamentals of Spintronics in Metal and Semiconductor Systems

Abstract

5.1 Introduction Spintronics is a new paradigm for electronics which utilizes the electron's spin in addition to its charge for device functionality [1, 2]. The primary areas for applications or potential applications are information storage, comput-ing, and quantum information. In terms of materials, the study of spin in solids now includes metallic multilayers [1], inorganic semiconductors [2, 3], transition metal oxides [4, 5], organic semiconductors [6, 7, 8, 9, 10], and carbon nanostructures [11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22]. The diversity of materials studied for spintronics is a testament to the advances in synth-esis, measurement, and interface control that lie at the heart of nano-electro-nics. In terms of technology, the discoveries of giant magnetoresistance (GMR) [23], tunneling magnetoresistance (TMR) [24], and spin torque [25] in metallic multilayers have led to significant advances in high-density hard drives and non-volatile random access memory. Advances in semiconductor spintronics [3] including the observation of long spin coherence times and the demonstration of spin manipulation point toward potential applications in advanced computation such as reconfigurable logic and quantum informa-tion processing. This tutorial is intended for graduate students just starting in the field of spintronics and for experts in other fields. Our goal is to cover some of the key ideas in spintronics and to present the material in an intuitive and pedagogical manner. We provide ''back of the envelope'' calculations when-ever possible. Due to the quantum mechanical nature of spin, some of the calculations require a working knowledge of quantum mechanics, so a short appendix is provided to review some of the quantum mechanical properties of spin.