From childhood, we are taught that the world exists in three physical dimensions. It’s true, for the most part, but it goes beyond something quite fascinating: the strange two-dimensional world of nanoscale materials, such as graphene “wonder material.”
Graphene and its single-layer counterparts actually exist in three dimensions, though barely – sitting right on the edge, atomically. That’s because the so-called 2D materials have a single thickness, embodying an incredible structural thinness, which gives them all kinds of strange powers.
We see this in the formidable strength of graphene and in the way it approaches superconductivity.
Things get even weirder when graphene befriends: stack sheets of this two-dimensional material in a three-layer, three-atom sandwich and a rare form of magnetism is revealed.
Now, in a new study led by physicists at Cambridge University, scientists have performed the same type of magnetic exploitation with a different two-dimensional material called iron phosphorus trisulfide (FePS).3).
(University of Cambridge)
Above: Illustration of the magnetic structure of iron-phosphorus trisulfide (FePS3), a two-dimensional material that undergoes a transition from an insulator to a metal when compressed.
FePS3 it is not the same as graphene – which is composed of a single layer of carbon atoms – but is often referred to as “magnetic graphene”, due to its mysterious capabilities at ultra-thin, layered dimensions.
In a previous study by some of the same researchers, the team found that when they crushed layers of FePS3 they were subjected to high levels of pressure, the material going from being an insulator, preventing the flow of electrons, to a metallic state where it became conductive.
But researchers still do not fully understand what underlies the magnetic behavior of this “magnetic graphene” under pressure, because it was expected that FePS3 it would cease to be magnetic when it enters the metallic state.
“The missing piece, however, remained magnetism,” says quantum physicist Matthew Coak.
“Without experimental techniques capable of probing the signatures of magnetism in this material at such high pressures, our international team had to develop and test our new techniques to make this possible.”
According to new research, FePS3 it keeps its magnetism under extremely high pressure due to a recently discovered type of magnetism that still exists during the metal phase.
“To our surprise, we found that magnetism survives and is, in a way, strengthened,” said researcher and lead physicist Siddharth Saxena, a group leader at Cavendish Laboratory in Cambridge.
“This is unexpected, because electrons that move freely in a new conductive material can no longer be trapped in their parent iron atoms, generating magnetic moments there – unless the conduction comes from an unexpected source.”
Although we do not yet have all the answers to what is happening here, during compression the “rotation” of electrons in the material seems to be a source of magnetism – and the phenomenon can be adjusted depending on how much FePS pressure3 is subject.
While the results contradict previous observations about how this material should behave, the surprises found here suggest that we may be able to further modify magnetic graphene and its kind – potentially finding materials that support superconductivity due to these shapes. exotic magnetism, we still do not fully understand them.
“We don’t know exactly what’s happening at the quantum level, but at the same time we can manipulate it,” says Saxena.
“It’s like those famous ‘unknown unknowns’: we’ve opened a new door to the properties of quantum information, but we don’t know yet what those properties might be.”
The findings are reported in Physical review X.