Researchers from the University of Washington and the Massachusetts Institute of Technology have discovered a two-dimensional magnetized material for the first time.
As reported in Nature, the material known as chromium triiodide (CrI3) is highly magnetic even when it’s in a 2D configuration. This particular object is part of a class of materials called monolayers, structures formed by a single atomic layer. Never before has a 3D substance retained its magnetic properties once turned into a 2D layer.
"What we have discovered here is an isolated 2D material with intrinsic magnetism, and the magnetism in the system is highly robust," Professor Xiaodong Xu, from the University of Washington, said in a statement. "We envision that new information technologies may emerge based on these new 2D magnets."
Bulky magnetic materials are called ferromagnetic. Their magnetism is derived from the alignment of electrons in the material. If you imagine that each electron is a tiny magnet, the substance is only magnetic if all the electrons point in the same way, otherwise the effect will cancel out.
In ferromagnetic substances, the electrons strongly influence each other, so it’s not surprising that once most of the atoms are removed, the properties are suddenly different. And this is why such a discovery might have far-reaching consequences.
"You simply cannot accurately predict what the electric, magnetic, physical or chemical properties of a 2D monolayer crystal will be based on the behavior of its 3D bulk counterpart," said co-lead author and UW doctoral student Bevin Huang.
The construction of this monolayer is surprisingly simple. The necessary material is a 3D sample of chromium triiodide and your standard sticky tape.
"Using Scotch tape to exfoliate a monolayer from its 3D bulk crystal is surprisingly effective," said co-lead author and UW doctoral student Genevieve Clark. "This simple, low-cost technique was first used to obtain graphene, the 2D form of graphite, and has been used successfully since then with other materials."
This research clearly demonstrates that magnetism can also happen in this 2D material and has the potential to be used in many fields where light magnetic structures are required, such as computers and mobile phones.
The team also discovered that while a one-layer version is ferromagnetic, a two-layer set up is not. Three layers is once again ferromagnetic, so it's likely that there’s a connection between the magnetic properties and the number of layers, although they are not sure what it is yet.
The team is also investigating heterostructures, materials made of two different monolayers that could provide a “best-of-both” worlds technological scenario.
"Heterostructures hold the greatest promise of realizing new applications in computing, database storage, communications and other applications we cannot even fathom yet," concluded Xu.
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