Spin-Charge-Lattice Coupling through Multi-Magnon Excitations in Multiferroic BiFeO3
M. O. Ramirez, A. Kumar, S. A. Denev, Y. H. Chu, J. Seidel, L. Martin, S-Y. Yang, R. C. Rai, X. Xu, J. F. Ihlefeld, N. Podraza, E. Saiz, S. Lee, J. Klug, S. W. Cheong, M.J. Bedzyk, O. Auciello, J. L. Musfeldt, D. G. Schlom, R. Ramesh, J. Orenstein, J. Musfeldt, A. Litvinchuk and V. Gopalan, Appl. Phys. Lett., 94, 161905 (2009). PDF
Spin-charge-lattice coupling mediated by multimagnon processes is demonstrated in multiferroic BiFeO3. Experimental evidence of two- and three-magnon excitations as well as multimagnon coupling at electronic energy scales and high temperatures are reported. Temperature dependent Raman experiments show up to five resonant enhancements of the two-magnon excitation below the Néel temperature. These are shown to be collective interactions between on-site Fe d-d electronic resonance, phonons, and multimagnons.
FIG. 2. (Color online) (a) Absorption spectrum obtained for a 100 nm BiFeO3 film on DyScO3(110). Solid lines are fits to the parameterized dielectric function at 5 K. (b) (Left axis) Energy position, ETL. Also shown are resonance conditions at Ti * (i=1–5) and TN involving the Raman excitation wavelength Eexc, Tauc–Lorentz energy, ETL, one- and two-magnon and phonons Ω1, Ω2, and Ω3. (Right axis) Integrated intensity ratio between the two-magnon and two-phonon Raman overtones as a function of temperature.