R&D: Progress Toward Picosecond On-Chip Magnetic Memory

Applied Physics Letters has published an article written by Debanjan Polley, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA, and Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA, Akshay Pattabi, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA, Jyotirmoy Chatterjee, Fraunhofer IPMS, An der Bartlake 5, 01109 Dresden, Germany, Sucheta Mondai, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA, Kaushalya Jhuria, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA, and Université de Lorraine, CNRS, IJL, Nancy, France, Hanuman Singh, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA, Jon Gorchon, Université de Lorraine, CNRS, IJL, Nancy, France, and Jeffrey Bokor, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA, and Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA

Abstract: “We offer a perspective on the prospects of ultrafast spintronics and opto-magnetism as a pathway to high-performance, energy-efficient, and non-volatile embedded memory in digital integrated circuit applications. Conventional spintronic devices, such as spin-transfer-torque magnetic-resistive random-access memory (STT-MRAM) and spin–orbit torque MRAM, are promising due to their non-volatility, energy-efficiency, and high endurance. STT-MRAMs are now entering into the commercial market; however, they are limited in write speed to the nanosecond timescale. Improvement in the write speed of spintronic devices can significantly increase their usefulness as viable alternatives to the existing CMOS-based devices. In this article, we discuss recent studies that advance the field of ultrafast spintronics and opto-magnetism. An optimized ferromagnet–ferrimagnet exchange-coupled magnetic stack, which can serve as the free layer of a magnetic tunnel junction (MTJ), can be optically switched in as fast as ∼3 ps. Integration of ultrafast magnetic switching of a similar stack into an MTJ device has enabled electrical readout of the switched state using a relatively larger tunneling magnetoresistance ratio. Purely electronic ultrafast spin–orbit torque induced switching of a ferromagnet has been demonstrated using ∼6 ps long charge current pulses. We conclude our Perspective by discussing some of the challenges that remain to be addressed to accelerate ultrafast spintronics technologies toward practical implementation in high-performance digital information processing systems.“

Acknowledgements
This work was supported by ASCENT, one of six centers in JUMP, a Semiconductor Research Corporation (SRC) program also sponsored by DARPA (instrumentation and data acquisition). This work was also supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02–05-CH11231 within the Nonequilibrium Magnetic Materials Program (MSMAG) (theoretical analysis). We also acknowledge support by the National Science Foundation Center for Energy Efficient Electronics Science and the Berkeley Emerging Technology Research (BETR) Center (instrumentation and data acquisition).