Experimental evidences

Ramirez, M.O, A Kumar, S.A Denev, Y.H Chu, J Seidel, L.W Martin, S.-Y Yang, R.C Rai, X.S Xue, J.F Ihlefeld, N.J Podraza, E Saiz, S Lee, J Klug, S.W Cheong, M.J Bedzyk, O Auciello, D.G Schlom, J Orenstein, Ramamoorthy Ramesh, J.L Musfeldt, A.P Litvinchuk, and V Gopalan. "Spin-charge-lattice coupling through resonant multimagnon excitations in multiferroic BiFe O3." Applied Physics Letters 94 (2009).