A multidisciplinary team from BSMA (groups of Alain Jonas, Bernard Nysten and Luc Piraux, with principal researchers Ronggang Cai and Vlad Antohe), in collaboration with Zhijun Hu from Soochow University (China) – a former post-doc from BSMA, fabricated a composite multiferroic layer wherein electrical information can be stored by a magnetic field. The layer offers new opportunities for data storage and remote actuation. Published in Advanced Materials
Ferromagnetic materials are currently used for permanent data storage in memory devices; the information is stored in the magnetization vector of small magnetic particles oriented in specific directions by external magnetic fields. Likewise, ferroelectric materials can be used for storing permanent information by an electric field, the direction of the electric polarization now being the storage element. These two classes of materials are often considered as belonging to two different worlds; however, an intersection exists corresponding to magnetoelectric materials, in which both ferromagnetism and ferroelectricity coexist.
In magnetoelectric materials, it is theoretically possible to write electrically-stored information by a magnetic field, or magnetically-stored information by an electric field. This opens interesting opportunities for designing new memory architectures or sensors. However, the coupling of ferromagnetism and ferroelectricity is most often weak in magnetoelectric materials, and writing magnetically an electrical information has been so far limited to low temperatures, or relatively complex inorganic materials.
Now, a multidisciplinary team from IMCN (Bio & Soft Matter) reports in Advanced Materials (http://dx.doi.org/10.1002/adma.201604604) on a regularly-nanopatterned layer made of a continuous ferroelectric plastic with embedded ferromagnetic metallic nanopillars. In this layer, the orientation of the electric polarization of the polymer can be flipped by applying a magnetic field in the presence of an aiding electric field. This happens at room temperature, and is mediated by internal stresses in the polymer building upon applying the magnetic field.
Not only is the room-temperature operation of this material of interest; its ease of fabrication, which involves relatively simple molding and electrodeposition operations, and the resulting regularly nanopatterned structure of the layer, are both attractive for practical applications. This being said, further research will be needed to fully understand the complex role of internal stresses in the magnetoelectric effect of the composite layer. Also intriguing is the relaxation of the material resulting from the motion of segments of the polymer chains under the action of electric and magnetic fields. But beyond this complexity, the study shows that new properties and coupling effects may arise when properly controlling the arrangement of well-known materials into composite nanostructures