Controlling Magnetism with an Electric Field
Researchers at the NSF-funded Nanosystems Engineering Research Center (ERC) for Translational Applications of Nanoscale Multiferroic Systems (TANMS), led by the University of California Los Angeles (UCLA), have discovered a way to control magnetism with an electric field, a very difficult task due to fundamental differences in these physical phenomena. By creating artificially engineered structures in which the direction of magnetization is rotated when an electric field is applied, the TANMS team achieved a 180-degree rotation—a feat previously considered impossible.
Demonstrating a novel approach to use electric fields to control the direction of magnetism potentially paves the way to future low-energy-consumption data storage technology; by replacing electric currents with electric fields, a few orders of magnitude lower energy would be consumed during the write process. When commercially realized, this scientific advance has the potential to completely revolutionize information storage technologies, possibly eliminate this element from impacting the footprint of batteries, and relieve future energy dissipation concerns in microchips.
It is now well recognized that energy dissipation in microchips could ultimately restrict the downsizing of physical dimensions that has fueled exponential growth of microelectronics and communications. Further, as the use of electronic components in daily life increases dramatically, energy dissipation in electronic devices plays an increasingly significant role—larger than previously contemplated—hence the focus on controlling magnetism with an electric field.
The need for electric field control of magnetism was realized early, and extensive research has gone into that need because the rationale for avoiding use of current is intuitive—namely, whenever current is applied to create a magnetic field or spin transfer torque, a significant amount of energy is dissipated in the current-carrying wire itself simply in the form of Joule heating. Multiple researchers have pointed out that actual dissipation in reorientation of magnets is extremely small, usually on the order of a few tens of kBT (an energy level), whereas the dissipation in a wire is many millions of kBT (i.e., enormous energy-level differences that have not been adequately addressed).
Using an electric field instead of electric currents to control the magnetic state requires special types of materials that can sustain an electric field (i.e., insulators) and also be magnetic. In this demonstration (see figure), TANMS researchers engineered a magnetic layer ( a spin valve) on top of a multiferroic (a magnetic ferro-electric insulator) to enable electric field control of the magnetism and thus be the first to rotate magnetization 180 degrees with the application of an electric field.
This work was published in the premier scientific journal, Nature. The effort required a collaborative team consisting of many experts, including theorists, researchers who make the artificially engineered structures, researchers who could explore switching of the magnetization with sophisticated x-ray probes, and physicists who could carry out the detailed magnetic measurements.