In situ Transmission Electron Microscopy (TEM) techniques can potentially fill in gaps in the current understanding interfacial phenomena in complex oxides. Select multiferroic oxide materials, such as BiFeO 3 (BFO), exhibit ferroelectric and magnetic order, and the two order parameters are coupled through a quantum-mechanical exchange interaction. The magneto-electric coupling in BFO allows control of the ferroelectric and magnetic domain structures via applied electric fields. Because of these unique properties, BFO and other magneto-electric multiferroics constitute a promising class of materials for incorporation into devices such as high-density ferroelectric and magnetoresistive memories, spin valves, and magnetic field sensors. The magneto-electric coupling in BFO is mediated by volatile ferroelastically switched domains that make it difficult to incorporate this material into devices.To facilitate device integration, an understanding of the microstructural factors that affect ferroelastic relaxation and ferroelectric domain switching must be developed. In this article, a method of viewing ferroelectric (and ferroelastic) domain dynamics using in situ biasing in TEM is presented. The evolution of ferroelastically switched ferroelectric domains in BFO thin films during many switching cycles is investigated. Evidence of partial domain nucleation, propagation, and switching even at applied electric fields below the estimated coercive field is revealed. Our observations indicate that the occurrence of ferroelastic relaxation in switched domains and the stability of these domains is influenced the applied field as well as the BFO microstructure. These biasing experiments provide a real time view of the complex dynamics of domain switching and complement scanning probe techniques. Quantitative information about domain switching under bias in ferroelectric and multiferroic materials can be extracted from in situ TEM to provide a predictive tool for future device development.
Bibliographical noteFunding Information:
The work at Drexel (MLT and CRW) was supported by the National Science Foundation through contract CMMI-1031403 and the Office of Naval Research through contract N00014-1101-0296. The use of the Centralized Research Facilities in the College of Engineering at Drexel University and assistance from staff scientist Dr. CL Johnson are gratefully acknowledged. At UIUC, JK and LWM acknowledge the support of the Office of Naval Research under Grant No. N00014-10-10525 and ARD and LWM acknowledge support from the Army Research Office under Grant No. W911NF-10-1-0482 . Experiments at UIUC were carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, which are partially supported by the U.S. Department of Energy under grants DE-FG02-07ER46453 and DE-FG02-07ER46471 .
- Coercive field
- Domain switching
- In situ TEM