Tutorial details nanoscale devices that couple electric and magnetic fields via strain

Composites made of both ferromagnetic and ferroelectric materials hold promise for many applications, from more sensitive medical imaging to low-power magnetic disk reading. To date, researchers have struck upon many composite materials that couple electric and magnetic fields together via mechanical strain, leveraging the interplay between piezoelectricity and its cousin magnetostriction. But questions remain about how to fabricate nanoscale versions of such composites — a recipe that could ultimately result in much stronger coupling due to the higher surface-area-to-volume ratios of nanostructures.

A detailed tutorial by Viehland et al. examines the tradeoffs present in state-of-the-art techniques for assembling such multiferroic nanocomposites, and discusses the microscopy methods currently used for their characterization. It also suggests possible ways to assemble nanocomposites into larger structures in the future.

The authors highlight several approaches to creating nanoscale multiferroics, including chemical self-assembly of nanoparticles using DNA tags and various deposition and growth techniques. They note that thin nanotubes or fibers featuring a coupled core and shell may offer the best chance for strong coupling because they don’t sit atop a substrate that can disrupt the mechanical link between the two materials. The tutorial also explains that RNA could potentially be a more flexible chemical handle than DNA for assembling larger structures, especially if it’s necessary to make adjustments to the geometry.

Although much progress has been made recently on synthesizing such nanocomposites, author Gopalan Srinivasan said that there are still fundamental questions that need to be addressed. “The theory is in its infancy,” Srinivasan said. “So there is a lot that needs to be done as far as the theory is concerned.”

Source: “Tutorial: Product properties in multiferroic nanocomposites,” by Dwight Viehland, Jie Fang Li, Yaodong Yang, Tommaso Costanzo, Amin Yourdkhani, Gabriel Caruntu, Peng Zhou, Tianjin Zhang, Tianqian Li, Arunava Gupta, Maksym Popov, and Gopalan Srinivasan, Journal of Applied Physics (2018). The article can be accessed at https://doi.org/10.1063/1.5038726 .