European Spallation Source AB: Opposites Repel: ESS Scientist Discovers New Magnetic Phenomenon
STOCKHOLM--(BUSINESS WIRE)--For the first time, a novel magnetic state has been discovered, where the most basic concept of magnetism - that opposites attract - does not hold true. The phenomenon has been discovered and described by an international team of scientists lead by ESS Director for Science Dimitri Argyriou. The discovery holds promise for tomorrow's memory and sensor technology, enabling devices from phones to cars. The finding was reported in Nature Materials.
Phones, cars, TVs and kitchen appliances - most of the tools we use have small computers inside, and they all require memory. Product development proceeds at breakneck pace, and the computers have to be ever smaller, smarter, more energy efficient. In pursuit of tomorrow's data-handling technology, researchers at the European Spallation Source have unearthed a novel magnetic phenomenon.
No one can say what the next big breakthrough in data-handling technology will be, but a class of materials called multiferroics are promising candidates. One such material is terbium ferrite, which can store information so that it can be written with electricity and read magnetically, at a low energy cost. This may revolutionise memory and sensor technology - but a lot of research is required before the concept can be used in applications.
An international research team lead by Dimitri Argyriou, Director for Science at ESS, Sweden, has used neutrons to probe the inner workings of terbium ferrite. They found that at an atomic scale, the atoms arrange themselves in a grid of microscopic domains, each of which behaves like a small bar magnet. These magnets do not line up in the same direction, as one might expect. Instead, adjacent domains have opposite magnetic directions, placing north next to north and south next to south. The scientists were also surprised by the overall domain structure: they are unexpectedly large (albeit on a microscopic scale) and display extremely sharp domain boundaries.
- I was expecting domains perhaps 30 times smaller than what we observed, says Dimitri Argyriou. And the domain boundaries are exceptionally sharp - I've never seen anything like it. The structure shouldn't be stable, and yet it is.
Pursuing this mystery, the team of professor Maxim Mostovoy, a theoretical physicist at Groningen University, the Netherlands, provided a surprising insight. The unusual structure observed - large domains with sharp domain walls and alternately arranged magnetic moments - is stabilized by a novel magnetic phenomenon. Surprisingly, the opposite poles of a domain repel each other. Rather than red attracting white and red repelling red as with bar magnets, in terbium ferrite, opposites repel.
– Our discovery has many implications, says Maxim Mostovoy. We think that this interplay between iron and terbium atoms can be used to make new, more versatile multiferroics that can cover the increasing demands of lean technology with low power consumption.
This discovery previews the discoveries that ESS, the European facility for research with neutrons under development in southern Sweden, will bring.
– Without neutrons, this discovery would have passed us by, says Dimitri Argyriou. We need more powerful neutron sources in order to probe deeper into such new states of matter. Once built, ESS will help us unearth new phenomena like this one, which remain hidden from us today. This is one example of the many new things a facility like ESS will help us discover, not only in magnetic materials, but in a broad range of fields of science and technology.