Soft antiphase tilt of oxygen octahedra in the hybrid improper multiferroic Ca3Mn1.9Ti0.1 O7

Feng Ye, Jinchen Wang, Jieming Sheng, C. Hoffmann, T. Gu, H. J. Xiang, Wei Tian, J. J. Molaison, A. M. Dos Santos, M. Matsuda, B. C. Chakoumakos, J. A. Fernandez-Baca, X. Tong, Bin Gao, Jae Wook Kim, S. W. Cheong