Skyrmion materials for spintronics

点击翻译按钮获取中文摘要

A global network of data centres powers the free access to news, social media, information and education that we take for granted. These data centres, which form part of the Internet's infrastructure, are made possible by magnetic recording technology that now stores the vast majority of the world's knowledge. However, both silicon technology and hard drives have recently seen the end of decades of exponential improvements in size and speed due to fundamental materials limitations. Improvements in energy efficiency will have important implications for the energy usage of data centres, which already consume approximately 2% of the total electricity in North America, as well as cell phones, portable electronics and the forecasted exponential growth of wearable electronics.******As one of the leading groups in the world in chiral magnetic thin film research, my group is positioned to yield new solutions to the technological demands of highly energy-efficient, high-speed magnetic memories. Unlike conventional visions of storage media where bits of information are stored in microfabricated transistors on flash drives, or on the large spinning platters in magnetic hard disk drives, chiral based magnetic memories will store information in nanoscale cylindrical magnetic textures skyrmions that naturally form in magnetic materials with particular crystal symmetries. Skyrmion memories would encode information over 1000 times faster than flash memory and be moved by currents 100,000 times smaller than conventional magnetic domains. One of the major obstacles to using skyrmion materials in practical devices is that skyrmions in most materials only form at temperatures below room temperature. This proposal seeks to discover new materials that produce skyrmions well above room temperature by using high-throughput vacuum deposition methods. Using combinatorial sputtering facilities at Dalhousie University, hundreds of alloy compositions can be grown on a single substrate. X-ray analysis will enable rapid screening of the alloys to identify those compositions with the right crystal symmetry, and electrical measurements will determine their magnetic ordering temperature. The best candidate materials will then be synthesized in atomically flat, single-crystal form by molecular beam epitaxy and the magnetic structures will be imaged at the nanoscale with electron and scanning probe microscopies.******By tuning the alloy composition, the size of the skyrmions will be controlled to understand the fundamental interactions that produce them. Just as bubbles nucleate from the edges of a pot of boiling water, skyrmions nucleate from film interfaces and edges. We can then control this nucleation by the choice of materials we deposit on the film surfaces. Skyrmions will then be pushed through nanofabricated wires by using electrical currents to develop new skyrmion magnetic memories.