Study Opens Route to Ultra-Low-Power Microchips

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“This is really a significant breakthrough,” says Chris Leighton, the Distinguished McKnight University Professor in the Department of Chemical Engineering and Materials Science at the University of Minnesota, who was not involved in this work. “There is currently a great deal of interest worldwide in controlling magnetic materials simply by applying electrical voltages. It’s not only interesting from the fundamental side, but it’s also a potential game-changer for applications, where magnetic materials are used to store and process digital information.”

Leighton says, “Using hydrogen insertion to control magnetism is not new, but being able to do that in a voltage-driven way, in a solid-state device, with good impact on the magnetic properties — that is pretty significant!” He adds, “this is something new, with the potential to open up additional new areas of research. … At the end of the day, controlling any type of materials function by literally flipping a switch is pretty exciting. Being able to do that quickly enough, over enough cycles, in a general way, would be a fantastic advance for science and engineering.”

Essentially, Beach explains, he and his team are “trying to make a magnetic analog of a transistor,” which can be turned on and off repeatedly without degrading its physical properties.

Just Add Water

The discovery came about, in part, through serendipity. While experimenting with layered magnetic materials in search of ways of changing their magnetic behavior, Tan found that the results of his experiments varied greatly from day to day for reasons that were not apparent. Eventually, by examining all the conditions during the different tests, he realized that the key difference was the humidity in the air: The experiment worked better on humid days compared to dry ones. The reason, he eventually realized, was that water molecules from the air were being split up into oxygen and hydrogen on the charged surface of the material, and while the oxygen escaped to the air, the hydrogen became ionized and was penetrating into the magnetic device — and changing its magnetism.

The device the team has produced consists of a sandwich of several thin layers, including a layer of cobalt where the magnetic changes take place, sandwiched between layers of a metal such as palladium or platinum, and with an overlay of gadolinium oxide, and then a gold layer to connect to the driving electrical voltage.

The magnetism gets switched with just a brief application of voltage and then stays put. Reversing it requires no power at all, just short-circuiting the device to connect its two sides electrically, whereas a conventional memory chip requires constant power to maintain its state. “Since you’re just applying a pulse, the power consumption can go way down,” Beach says.

The new devices, with their low power consumption and high switching speed, could eventually be especially useful for devices such mobile computing, Beach says, but the work is still at an early stage and will require further development.

“I can see lab-based prototypes within a few years or less,” he says. Making a full working memory cell is “quite complex” and might take longer, he says.

The work was supported by the National Science Foundation through the Materials Research Science and Engineering Center (MRSEC) Program.

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