GUEST EDITORIAL — RECENT PROGRESS IN SPINTRONIC DEVICES YIMING HUAI * ,‡ , PEDRAM KHALILI AMIRI †,§ and KANG L. WANG †,¶ * Avalanche Technology, Fremont, CA, USA † Department of Electrical Engineering University of California, Los Angeles, CA, USA ‡ yiming@avalanche-technology.com § pedramk@ucla.edu ¶ wang@ee.ucla.edu Published 9 November 2012 The past three decades have witnessed an explosive growth of research activities and discoveries in the area of spintronics. At their heart, spintronic device technologies are based on physical phenomena that allow electrical signals (currents and voltages) to interact directly with spins in nanomagnetic struc- tures, i.e., where magnetic and transport properties are directly coupled. Spintronics as a ¯eld of science has exhibited a remarkable rate of new fundamental discoveries, which in turn have been translated into industrial applications at a very rapid pace. The most prominent initial examples were the dis- coveries of the giant magnetoresistance (GMR) (by Albert Fert and Peter Grünberg, who won the Nobel Prize for Physics in 2007) and tunneling magne- toresistance (TMR) e®ects, which established a technologically signi¯cant (i.e., large) relationship between electrical resistance and magnetization states of nanostructures. These fundamental dis- coveries were adopted very quickly into hard disk drive read heads, revolutionizing the data storage industry. They also set the stage for the emergence of magnetic-¯eld-switched (toggle) magnetoresistive random access memory (MRAM), which has been in production for several years at the time of this writing. The subsequent discovery of the spin- transfer torque (STT) e®ect greatly expanded the range of applications of — as well as fundamental phenomena of interest in — spintronic devices, with the most notable example being the emergence of STT-MRAM technology. With the recent industrial adoption and emergent prospects of commercial STT-MRAM products to be introduced in the market, fundamental studies into novel phenomena for future generations of spintronic devices continue at a very fast pace. A common challenge is enhancing the energy e±ciency of spin- tronic devices beyond that delivered by the STT e®ect, e.g., through the use of new physical mech- anisms such as electric-¯eld-control of magnetism, the use of nontraditional spin injection methods such as the spin Hall e®ect, and utilization of the newly discovered spin-momentum locking of topological insulators for e±cient spin current injection. Another set of recent discoveries of interest are in the area of spin caloritronics and the spin Seebeck e®ect, i.e., investigating the interaction of thermal e®ects (phonons) with magnetic phenomena and transport in nanostructures. Overall, it is no exaggeration to state that the ¯eld of spintronics — in terms of both its industrial relevance and its rate of fundamental discoveries — is at an in°ection point, with exciting new results not only hinting at the signi¯cant future possibilities for fundamental study, but also showing SPIN Vol. 2, No. 3 (2012) 1202001 (3 pages) © World Scienti¯c Publishing Company DOI: 10.1142/S2010324712020018 1202001-1 SPIN 2012.02. Downloaded from www.worldscientific.com by "UNIV OF CALIFORNIA,LOS ANGELES" on 03/27/13. For personal use only.