| Posted: Jul 25, 2014 | |
New class of materials could power memory devices |
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| (Nanowerk News) A new phase of matter known as topological insulators, until recently known only for esoteric quantum-mechanical properties, might have a practical use in controlling magnetic memory and logic devices. | |
| A team of Cornell and Penn State University physicists has demonstrated for the first time that electrical currents flowing along the surface of topological insulators can exert a torque on an adjacent magnetic layer that is 10 times more efficient than any other known mechanism. This breakthrough provides a new strategy for making next-generation memory technologies that use the least possible energy and current. | |
| The research, led by Dan Ralph, the F.R. Newman Professor of Physics at Cornell, and Nitin Samarth of Penn State, is published online July 24 in the journal Nature ("Spin-transfer torque generated by a topological insulator"). The team used the topological insulator bismuth selenide (a combination of bismuth and selenium) for their experiments. | |
| Like conventional insulators, topological insulators do not allow current to flow through the material, but they are different because they are wrapped in a conducting surface. Electrons flowing on the surface also do something unique: The direction of an electron’s spin is always locked perpendicular to its direction of motion. This locking provides a means for the flow of an electrical current along the surface to produce a buildup of spin that can apply torque to an adjacent magnet. | |
| Ralph and colleagues are trying to develop new magnetic nonvolatile memory and logic devices. One of the main challenges in doing so is to find a way to quickly flip the devices’ magnetization using the least possible current. | |
| The new results show that electrical current flowing within a thin film of bismuth selenide – at room temperature no less – can be used for this purpose. | |
| The researchers caution that actual memory devices are a long way off, but the paper, Ralph noted, can be viewed as an exciting first step for a new branch of science. |
| Source: By Anne Ju, Cornell University | |
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