From childhood we are taught that the world exists in three physical dimensions. This is mostly true, but it skips something quite fascinating: the strange two-dimensional world of nanoscale material, such as the ‘miracle material’ graphene.
Graphene and its designed single-layer counterparts actually exist in three dimensions, although they are only rare – atomically speaking on the edge. This is because these so-called 2D materials are only one atom thick, containing an incredible structural thinness that gives them all sorts of strange forces.
We see this in the formidable strength of graphene and in the way it approaches superconductivity.
Things get even stranger as graphene makes friends: stacking sheets of this two-dimensional material in a three-layer, three-atom-high sandwich, and a rare form of magnetism are revealed.
Now, in a new study led by physicists from the University of Cambridge, scientists have drawn the same kind of magnetic performance with another 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 is not the same thing as graphene – which consists of a single layer of carbon atoms – but it is often called ‘magnetic graphene’, due to its mysterious capabilities against ultra-thin, low-layer dimensions.
In a previous study by some of the same researchers, the team found that when they flatten low FePS3 was under pressure, the material switched from an insulator, which obstructed the flow of electrons, to a metallic state where it became a conductor.
But researchers still do not fully understand what lies beneath the magnetic behavior of this ‘magnetic graphene’, as FePS was expected to3 would cease to be magnetic when going into the metal state.
“The missing piece, however, remained, the magnetism,” says quantum physicist Matthew Coak.
“With no experimental techniques capable of examining the signatures of magnetism in this material at such a high pressure, our international team had to develop and test our own new techniques to make it possible.”
According to new research, FePS3 retains its magnetism under extremely high pressure due to a newly discovered type of magnetism that still exists during the metal phase.
“To our surprise, we have found that magnetism survives and is amplified in some ways,” explains senior researcher and physicist Siddharth Saxena, group leader at the Cavendish Laboratory in Cambridge.
“This is unexpected, because the newly-free-floating electrons in a newly conductive material can no longer be attached to their older iron atoms, and generate magnetic moments there – unless the conduction comes from an unexpected source.
Although we do not yet have all the answers on what is happening here, it seems that the ‘rotation’ of the electrons in the material is a source of magnetism, and the phenomenon can be set depending on how much pressure FePS is3 is subject to.
Although the results reflect with previous observations of how this material should behave, the surprises found here suggest that we can adapt magnetic graphene and its kind even further – which may find materials that support superconductivity due to these exotic forms of magnetism we do not yet have. fully understood.
“We do not know exactly what is happening at quantum level, but at the same time we can manipulate it,” Saxena says.
“It’s like the famous ‘unknown unknowns’: we’ve opened a new door to quantum information properties, but we do not yet know what those properties could be.”
The findings are presented in Physical overview X.