Giant Spin-Driven Electric Polarization is Revealed in Promising Multiferroic
Multiferroic materials are important because their electrical and magnetic properties are coupled. Because BiFeO3 magneticallyorders below 640 K, it is one of two known room-temperature multiferroic materials. Recently, theorists at Oak Ridge National Laboratory discovered that the spin-driven electric polarization of BiFeO3 below its magnetic ordering temperature, TN, is much larger than in any other known multiferroic.
The spin-driven polarization below TN is produced by the rotation of the FeO6 octahedron and points opposite to the even larger pre-existing electric polarization above TN. Ironically, the large size of the pre-existing polarization has prevented direct observation of the giant spin-driven polarization. However, recent neutron diffraction measurements of the crystal parameters confirm the theoretical predictions, as shown in the figure.
This giant spin-driven polarization will allow the development of devices that control the magnetic properties of BiFeO3 with an electric field or control its electric properties with a magnetic field. The theoretical technique developed in this work can also be used to study the spin-driven electric polarizations in other technologically important multiferroic materials.
Jun Hee Lee and Randy S. Fishman, “Giant Spin-Driven Ferroelectric Polarization in BiFeO3 at Room Temperature,” Phys. Rev. Lett. 115, 207203 (2015). DOI: 10.1103/PhysRevLett.115.207203
For more information, contact Randy Fishman: firstname.lastname@example.org