Evidence for strong spin-lattice coupling in multiferroic R Mn ₂O ₅ (R=Tb,Dy,Ho) via thermal expansion anomalies

C. R. Dela Cruz, F. Yen, B. Lorenz, S. Park, S. W. Cheong, M. M. Gospodinov, W. Ratcliff, J. W. Lynn, C. W. Chu