Jun 2, 2011
Multiferroic nanofibres spun out for nanoscale sensing and actuation
Multiferroic materials such as bismuth ferrite (BiFeO3), which display co-existence of both electric and magnetic order parameters are of great scientific and technological interest. Typically, the bulk form of BiFeO3 exhibits weak saturation magnetization and weak ferroelectricity due to its non-stoichiometry and defects. Now, researchers report that nanostructured BiFeO3 in fibre form can display well defined ferroelectricity as well as ferromagnetism. This finding could be significant for the design of future nanoscale electronic devices such as sensors and actuators.
The team, which includes researchers from the University of Sydney, Australian National University, the University of Akron and the University of Wollongong, uses a sol-gel method in combination with electrospinning to assemble and organize the fine-grained structures of BiFeO3 into fibres. Electrospinning allows the researchers to control the size of BiFeO3 particles and collect aligned fibrous structures, which opens the door to building novel nanoscale electronic devices. The BiFeO3 fibres display sizeable M versus H hysteresis loops; that is, the fibres show ferromagnetism at room temperature. The non-linear M versus H relationship is accompanied by a coercivity of ~250 Oe and 1.34 emu/g saturation magnetization. The size of the individual particles in the fibres was ~30 nm, which is much smaller than the size of the spiral ordering (~62 nm). Hence, the fibres displayed ferromagnetic behaviour as opposed to weak magnetization displayed by bulk BiFeO3. Furthermore, the piezoresponse of the fibre was measured and the local polarization and domain structures within the fibres were determined.
The amplitude versus voltage loops recorded for the fibre display a butterfly shape, which is a typical characteristic of ferroelectric material. Thus, the ferromagnetic and ferroelectric behaviour of the fibre was confirmed.
More details can be found in the journal Nanotechnology.
About the author
The study was performed at the Centre for Advanced Materials Technology (CAMT), University of Sydney, Australia. Avinash Baji is a research associate funded by the Australian Research Council (ARC) and is currently working under the direct supervision of Prof. Yiu-Wing Mai. Prof. Mai is a professor and personal chair in mechanical engineering at the University of Sydney. The work is performed in collaboration with other research groups, including the Research School of Chemistry, Australian National University (Qing Li, Dr Yun Liu), the Department of Mechanical Engineering, University of Akron, US, (Prof. Shing-Chung Wong) and the Institute for Superconducting and Electronic Materials, University of Wollongong, Australia (Dr QW Yao).