This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: With the rapid spread of cloud computing, artificial intelligence and data centers, global energy consumption is rising to new heights. A promising way to reduce this burden is to develop memory devices that store information magnetically yet are written using electric fields.
Magnetic memories are nonvolatile, meaning stored information is retained without a power supply. However, the conventional method of writing to magnetic memory relies on the magnetic field induced by electric currents, which inevitably dissipates energy as Joule heat. Instead, using an electric field to switch the magnetic state would provide a pathway to significantly more energy-efficient memory devices.
Multiferroic materials, which simultaneously display both electric and magnetic order, are a potential route toward this goal. Because both types of order are coupled, applying an electric field to these materials can cause their magnetic state to flip. For these materials to find use in real memory devices, however, their behavior at nanometer scales must be demonstrated.
At those dimensions, materials can develop complex polarization arrangements called topological domain structures, whose relationship to magnetic behavior is less clear. To address this knowledge gap, a research team led by Assistant Professor Kei Shigematsu of the Institute of Science Tokyo (Science Tokyo), Japan, along with JSPS Postdoctoral Fellow Koomok Lee and Professor Masaki Azuma, also of the institute, studied the electric and magnetic behavior of nanoscale structures made from the multiferroic material BiFe0.9Co0.1O3 (BFCO). They worked in collaboration with the Sumitomo Chemical Next-Generation Eco-Friendly Devices Collaborative Research Cluster, Institute of Integrated Research, Science Tokyo, and the Kanagawa Institute of Industrial Science and Technology (KISTEC), Japan.
Their findings were published in the journal Science Advances. The team fabricated arrays of BFCO nanodots, each roughly 190 nm in diameter. Using two complementary imaging techniques—piezoresponse force microscopy to map electric polarization and scanning nitrogen-vacancy center magnetometry to detect magnetic fields—they visualized both the electric and magnetic domain structures of the nanodots before and after applying an electric field.
Each nanodot originally exhibited a "center-convergent" electric polarization structure, where polarization vectors all pointed inward toward the center. Applying an electric field transformed this original state into a "center-divergent" structure, with polarization vectors pointing outward. This restructuring was accompanied by a reversal of magnetization in both the in-plane and out-of-plane directions within each nanodot.
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