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The Best Sandwiches are Not the Most Perfect Sandwiches

Surprises in the Atomic-Scale Chemical Structure of Next-Generation Magnetic Devices Researchers around the world are trying to develop computer memory that retains information without power — the key to “instant-on” computers. One of the leading contenders for this technology is a type of magnetic “sandwich,” known as a magnetic tunnel junction, made by separating two ultrathin magnets (here, CoFeB) with a few-atoms-thick insulator (here, MgO). Expecting that the best performance would come from atomically perfect sandwiches, researchers at Cornell developed a new technology to image the atomic-scale chemical structure of the sandwiches. Somewhat surprisingly, they found that the best devices were not perfect. Instead, the best devices were those in which some boron atoms escaped the magnets and crept into the insulator. (In the image at right, the mixture of green boron and red oxygen in the insulator leads to yellow patches in the center of the sandwich.) This surprising discovery points the way to the design of high-performance magnetic memory.

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This project is supported by U.S. National Science Foundation under the Materials Research Science and Engineering Centers (MRSEC) program. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the U.S. National Science Foundation or the participating institutions. This site is maintained collaboratively by principal investigators with NSF MRSEC awards, independent of NSF.