Physicists detect femtoscale atomic displacements in multiferroic materials

28 August 2011

An international team of physicists 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 functional materials known as multiferroics can develop magnetic order and a ferroelectric polarization simultaneously. Multiferroics are candidate materials for new classes of electronic devices. The discovery is published in the 2 September 2011 issue of Science.

A breakthrough in understanding materials for next-generation electronic devices

Multiferroic materials combine both a ferroelectric polarization and some form of magnetic order. If these two ordering phenomena are coupled then the material can be used in devices to control electrical signals by magnetic fields, and vice versa. Interest in multiferroics was ignited in 2003 by the discovery of a strong multiferroic coupling in the insulating compound terbium manganite (TbMnO3).

The team, including Oxford physicists Dr D. Prabhakaran and Professor Andrew Boothroyd, measured the interference between polarized X-ray photons undergoing both charge and magnetic scattering processes. They studied a single crystal of TbMnO3 grown in the Clarendon Laboratory, and were able to measure the displacements of specific atoms within the compound with an accuracy approaching one femtometre (10–15m), or 100,000 times smaller than the atoms themselves.

The new interference scattering technique has set a world record for the accuracy with which atomic displacements in solids can be measured. More significantly, the ability to identify the origin of ferroelectricity in different multiferroic materials is a major step forward in the design of multiferroics for practical applications.