Control of Ferroelastic Switching in Multiferroic Materials
Balke,1 S. Choudhury,2 S. Jesse,1 M. Huijben,3,4 Y.H.
L.Q. Chen,2 R. Ramesh,3 and
1 The Center for Nanophase Materials Sciences, Oak Ridge National
Laboratory, Oak Ridge, TN 37831
2 Department of Materials Science and Engineering, Pennsylvania State
University, University Park, PA 16802
3 Department of Materials Science and Engineering and Department of
Physics, UC Berkeley, CA 94720
4 Faculty of Science and Technology, MESA+ Institute for
University of Twente, P.O. BOX 217, 7500 AE, Enschede, The Netherlands
5 Department of Materials Science and Engineering, National Chiao Tung
University, Hsinchu 30010, Taiwan
We have demonstrated a new technique to guide the ferroelastic switching
process in bismuth ferrite, one of the most popular magnetoelectric
materials envisioned for memory and logic devices. Using the symmetry
breaking of a moving SPM probe, we can selectively write domains
which are otherwise thermodynamically equivalent but differ in magnetization
and strain. Remarkably, this control of polarization switching allows
for the creation of the first unambiguous ferroelectric closure domain
pattern, the precursor to the long-sought ferroelectric vortex state.
Realization of the next generation of magnetoelectric, strain-coupled,
and domain-wall based devices necessitates the control of polarization
switching in multiferroics with multiple possible polarization directions.
In rhombohedral ferroelectrics, application of an electric field
in the pseudocubic (001) direction can lead to 180° ferroelectric
switching or to 71° and 109° ferroelastic switching. While
the electrostatic energy gain is equivalent, the magnetic and strain
states and domain wall properties of the final structures are quite
different. In this research we illustrate the deterministic control
of ferroelastic switching in these materials using symmetry breaking
caused by a moving scanning probe. The fabrication of predefined
domain patterns is demonstrated through the creation of artificial
ferroelectric closure domains which are believed to be the precursors
to vortex domains (see Figure 1). This discovery enables a reliable
pathway for the design and creation of domain engineered magnetoelectric,
domain-wall based, and strain coupled devices.
More broadly, these results illustrate that mechanisms of phase transitions
leading to equivalent final states can be preferentially selected by
local stimulus. It was traditionally believed that only biological
systems can undergo multiple mechanisms with comparable energies, while
phase transitions in inorganic materials were limited to those between
only two states. Here, we demonstrate that deterministic selection
mechanisms can be understood and controlled at nanometer scales.
This work was published online in Nature Nanotechnology, DOI: 10.1038/NNANO.2009.293.
This research at Oak Ridge National Laboratory's Center for Nanophase
Materials Sciences was sponsored by the Scientific User Facilities
Division, Office of Basic Energy Sciences, U.S. Department of Energy
(NB, SJ, APB) and ORNL LDRD program (SVK, LQC). SC and LQC at Penn
State acknowledge the financial support of NSF under DMR-0213623,
DMR-0507146. NB acknowledges support from the Alexander von Humboldt
foundation. The theory work at Pennsylvania State University is also
supported by the Department of Energy Basic Sciences under DE-FG02-07ER46417
(L.Q.C.). Y.H.C. would like to acknowledge the support of the National
Science Council, Republic of China, under contract No. NSC 98-2119-M-009-019.
for highlight: “Deterministic control of ferroelastic
switching in multiferroic materials,” Nature Nanotechnology,