Vibronic Magnetoelectric Effects in the Bi-Based Multiferroics
P. Konsin and B. Sorkin
Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
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The detailed magneto-electron-lattice (vibronic) theory of ferroelectricity in the Bi-based multiferroics (BiFeO3 etc.) is developed further. The vibronic admixture of the empty oxygen 2p states to the Bi 6s lone electron pair state leads to ferroelectricity. These interactions are the driving and restoring forces of the structural phase transformations of the Bi-based multiferroics. The free energy of the BiFeO3-type multiferroics with the ferroelectric and the G-type antiferromagnetic phase transitions are derived. The Zeeman splitting and spin-transversal optical phonon couplings are also important.

DOI: 10.12693/APhysPolA.127.243
PACS numbers: 63.20.kd, 77.84.-s, 77.80.Bh, 77.80.-e