Nanoscale 'reactor' produces new compound

A team of physicists at the University of Groningen, Netherlands has discovered a new manganese compound that is produced by tension in the crystal structure of terbium manganese oxide, according to research published today in the journal Nature.

To create the new material, which experts have said could revolutionise nanoscale circuits, the Dutch research team grew a nanoscale layer of the terbium manganese oxide crystal on a thicker base layer of strontium titanium oxide.

“As has now become apparent, the domain wall can become a nanoscale chemical reactor

Lead researcher Beatriz Noheda

In doing this, the base layer affects the growth of the thinner layer - creating a ’domain wall’ that develops when pieces of growing crystal meet, the physicists said.

Through this reaction, the crystal structure comes under tensile stress in the wall.

Until recently, however, material scientists tried to prevent domain walls from occurring because of this tensile stress.

“Domain walls were seen as contamination,” said Beatriz Noheda, professor of functional nanomaterials at the University of Groningen, and study leader.

Noheda said that it has since become clear that “the tension in the crystal structure actually invested the material with new properties, and, as has now become apparent, the domain wall can become a nanoscale chemical reactor”.

Interestingly, the research team discovered that it was also possible to manipulate the number of domain walls that could be developed.

“Alongside controlling how many walls develop, a further considerable challenge was to analyse exactly what happens in a wall, as this is generally only one atom thick,” said Noheda.

To understand how the composition of the crystal in the walls had changed, the research team employed advanced atomic-resolution chemical analysis - discovering that in specific locations, a manganese atom had taken the place of a larger terbium atom.

Matching the results of this experiment, Maxim Mostovoy at the University of Groningen said: “A bond that has not yet been described occurs between five manganese atoms. We therefore see new chemistry in the domain wall.

“This makes the domain wall a kind of nanoscale chemical reactor. And we suspect that this kind of new bond will occur in all crystals with this zigzag structure” (see image).

The Dutch research team now intends to generate domain walls with the potential to form nanoscale circuits.