Magnetic memory retains information in magnetized states even when a device is not continuously powered, but conventional writing generally relies on a magnetic field generated by an electric current. That process also produces Joule heat. Electric-field switching in multiferroic materials could provide a lower-power alternative because these materials couple electric polarization and magnetic order, allowing a change in polarization to be accompanied by a change in magnetization. The central challenge is to establish that this behavior remains controllable when such materials are reduced to nanometer dimensions, where complex polarization configurations known as topological domain structures can emerge.

The research team, led by Assistant Professor Kei Shigematsu with JSPS Postdoctoral Fellow Koomok Lee and Professor Masaki Azuma, worked with the Sumitomo Chemical Next-Generation Eco-Friendly Devices Collaborative Research Cluster, the Institute of Integrated Research at Science Tokyo, and the Kanagawa Institute of Industrial Science and Technology. The team fabricated arrays of BFCO nanodots, each roughly 190 nanometers in diameter. It used two complementary imaging techniques to examine the nanodots before and after applying an electric field: piezoresponse force microscopy mapped local electric polarization, and scanning nitrogen-vacancy center magnetometry detected magnetic fields. Imaging both properties in the same individual structures allowed the researchers to associate changes in polarization with the accompanying magnetic reversal.

Each nanodot initially displayed a center-convergent electric-polarization structure, in which polarization vectors pointed inward toward its center. Applying an electric field changed this arrangement into a center-divergent structure, with the polarization vectors pointing outward. The restructuring coincided with reversal of magnetization in both the in-plane and out-of-plane directions. The reversal did not occur through a simple flip of individual electron spins. Instead, the magnetic moment rotated within the material’s easy plane—the preferred orientation for magnetization—as the polarization switched, moving the magnetization into its reversed configuration. Shigematsu said this mechanism enables complex but controllable magnetic configurations at nanoscale dimensions relevant to semiconductor devices.

The observations provide an experimental basis for magnetic-memory concepts in which information is written electrically and read magnetically. The authors note that, compared with current-based technologies such as spin-transfer-torque magnetic random-access memory, this approach could significantly reduce energy consumption. The multistate domain structure of a single nanodot could also in principle support more than one distinguishable magnetic configuration, offering a possible route to memory architectures beyond binary storage. These are prospective device implications rather than demonstrated memory performance: the experiment directly established electric-field-induced polarization switching and persistent magnetization reversal in BFCO nanodots, providing a concrete foundation for the design of next-generation, ultra-low-power magnetic-memory devices.

Subject of Research: Experimental electric-field control of magnetization in 190-nanometer BFCO multiferroic nanodots

Article Title: Nanoscale multiferroic materials open the path to efficient magnetic memory technology

Article References: Nanoscale multiferroic materials open the path to efficient magnetic memory technology. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: multiferroics, BFCO, magnetization reversal, electric-field switching, ferroelectric polarization, nanodots, magnetic memory, nitrogen-vacancy magnetometry, piezoresponse force microscopy, low-power electronics, Nanoscale, multiferroic