Mechanical Switching of Nanoscale Multiferroic Phase Boundaries

Tuning the lattice degree of freedom in nanoscale functional crystals is critical to exploit the emerging functionalities such as piezoelectricity, shape-memory effect, or piezomagnetism, which are attributed to the intrinsic lattice-polar or lattice-spin coupling. Here it is reported that a mechanical probe can be a dynamic tool to switch the ferroic orders at the nanoscale multiferroic phase boundaries in BiFeO3 with a phase mixture, where the material can be reversibly transformed between the soft tetragonal-like and the hard rhombohedral-like structures. The microscopic origin of the nonvolatile mechanical switching of the multiferroic phase boundaries, coupled with a reversible 180 degrees rotation of the in-plane ferroelectric polarization, is the nanoscale pressure-induced elastic deformation and reconstruction of the spontaneous strain gradient across the multiferroic phase boundaries. The reversible control of the room-temperature multiple ferroic orders using a pure mechanical stimulus may bring us a new pathway to achieve the potential energy conversion and sensing applications.National Science Foundation of China [51322207, 51332001, 11274045, 51472140, 11204230]; National Basic Research Program of China [2014CB920902, 2012CB619402]; U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [FG02-07ER46417]SCI(E)EIARTICLEjxzhang@bnu.edu.cn223405-34132