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CNR: Alamanacco della Scienza


N. 14 - 14 set 2011
ISSN 2037-4801

International info   a cura di Cecilia Migali


Observed the smallest atomic displacements

An international team of scientists has developed a novel X-ray technique for imaging atomic displacements in materials with unprecedented accuracy. They have applied their technique to determine how a recently discovered class of exotic materials - multiferroics - can be imultaneously both magnetically and electrically ordered. Multiferroics are candidate materials for new classes of electronic devices. The discovery, a major breakthrough in understanding multiferroics, is published in Science.
The authors comprise scientists from the European Synchrotron Radiation Facility (Esrf) in Grenoble (France), the University of Oxford and the London Centre for Nanotechnology, University College London.
Everybody is familiar with the idea that magnets are polarised with a north and a south pole, which is understood to arise from the alignment of magnet moments carried by atoms in magnetic materials. Certain other materials, known as ferroelectrics, exhibit a similar effect for electrical polarisation. The exotic 'multiferroic' materials combine both an ordered arrangement of atomic magnetic moments and ferroelectric polarisation, with a strong coupling between the two usually separate phenomena.
However, the origin of the electric polarisation in multiferroics has remained elusive until now. The team's work unambiguously shows that the electric polarisation in the multiferroic studied proceeds from the relative displacement of charges of different signs, rather than the transfer of charge from one atom to another.
The new interference scattering technique has set a world record for accuracy in absolute measurements of atomic displacements. Most significantly, identification of the origin of ferroelectricty in a multiferroic material is a major step forward in our understanding of multiferroics which may in the long term lead to the design of multiferroics for practical applications.

Fonte: Claus Habfast, European Synchrotron Radiation Facility (Esrf), tel. +33 666 662 384, email claus.habfast@esrf.fr

Per saperne di più: - www.esrf.eu/