Memory devices that store information use materials called ferroelectrics. Ferroelectrics have a property called polarization, where positive and negative charges are separated within the material even without an external electric field, and the direction of this polarization can be reversed by applying an external electric field. Information is stored as "0" or "1" based on the direction of polarization.
A research team led by Assistant Professor Shun Dekura at Tohoku University discovered a phenomenon called "plastic crystalline." This is a phenomenon where in a material which maintains its shape like a solid while its internal molecules rotate like a liquid, in response to the application of an external electric field to the material, the orientation and shape of the molecules are changed, and the material can maintain that state. The team focused on the plastic crystalline phase of an easily obtainable organic molecule with a simple structure called "succinonitrile." They precisely measured the electrical response when an external electric field was applied and observed a phenomenon called hysteresis, where the magnitude of polarization differs depending on the history of electric field strength changes. Since the way this phenomenon changes shows unique properties different from conventional ferroelectrics, they investigated its origin in detail and revealed that two different degrees of freedom of molecules—orientation and shape—are involved. They determined that this molecule takes two shapes: a gauche conformation where part of the elongated shape bends, and a trans conformation that extends straight, and when an external electric field is applied, not only do the molecular orientations align, but the molecular shapes also change.
This could lead to the realization of multi-value memory that can store more information than conventional binary memory, which takes "0" and "1" values, by switching both molecular orientation and shape. Furthermore, significant high-density and energy-saving improvements in information recording devices can be expected.
(Article: Masanori Nakajo)
