ERC Researchers Demonstrate First Repeatable Control of Magnetization in Multiferroic Structure
Researchers at the NSF-funded Nanosystems Engineering Research Center (ERC) for Translational Applications of Nanoscale Multiferroic Systems (TANMS), which is led by the University of California Los Angeles (UCLA), have demonstrated the first repeatable, deterministic, strain-coupled control of magnetization in any multiferroic structure. (Multiferroics address the limitations of using wires in very small electromagnetic devices, such as nanomotors.)
This achievement represents significant movement toward the ERC's goal to revolutionize the development of consumer electronics by engineering materials that optimize energy efficiency, size, and power output on the small scale. In this case the focus is on tiny motors. Understanding how to control magnetism in multiferroic structures could one day enable high-speed control of magnetic nanomotors that would provide orders of magnitude higher power density than any other motor of similar size.
Conventional electromagnetic motors do not scale down with size due to the poor scaling of resistance; this limitation makes it challenging to drive sufficient current in small-diameter wires to produce the needed magnetic fields. TANMS seeks to overcome limitations of the current-through-wire approach by using multiferroic materials, which react in a manner analogous to placing a voltage-controlled on-off switch on a permanent magnet.
The first step in developing a high-power nanomotor is to understand and demonstrate deterministic control of the magnetization state. However, applying an electric-field-induced strain can cause the magnetization to rotate statistically either +90 degrees or -90 degrees (like a coin flip) rather than only in one direction (deterministic). Therefore, the research community has continually expressed concern that the induced-strain process could not be deterministically controlled. This concern has been contradicted, experimentally and analytically, by the researchers' work, which showed that magnetization can be controlled deterministically with a properly designed strain process.
Deterministic control of rotation was verified by multiple sweeps of an electric field up and down as well as by modeling results; both methods showed the magnetization was repeatable, thereby demonstrating the first deterministic strain-coupled control of magnetization in any multiferroic structure. Substantial work remains to accomplish the ultimate goal of a nanoscale, multiferroic motor, but these recent results are a noteworthy step forward.