Magnets and magnetism help us in a number of ways in our everyday lives with storage in computers being one of the best examples. In a bid to achieve faster and efficient devices that rely on magnetism researchers have discovered that magnetism in the 2-D world of monolayers, or materials that are formed by a single atomic layer.
Researchers at University of Washington and the Massachusetts Institute of Technology proved that chromium triiodide, or CrI3 exhibits magnetic properties in its monolayer form. Atoms within monolayer materials are considered “functionally” two-dimensional because the electrons can only travel within the atomic sheet, like pieces on a chessboard.
To discover the properties of CrI3 in its 2-D form, researchers used Scotch tape to shave a monolayer of CrI3 off the larger, 3-D crystal form. Scientists effectively exfoliated a monolayer of CrI3 from its 3-D bulk crystal. This particular method was also used to obtain graphene, the 2-D form of graphite, and has been used successfully since then with other materials.
Scientists explain that in case of ferromagnetic materials, the aligned spins of electrons leave a telltale signature when a beam of polarized light is reflected off the material’s surface. This signature was detected in CrI3 using a special type of microscopy, which they say is the first definitive sign of intrinsic ferromagnetism in an isolated monolayer.
Surprisingly, in CrI3 flakes that are two layers thick, the optical signature disappeared. This indicates that the electron spins are oppositely aligned to one another, a term known as anti-ferromagnetic ordering.
Ferromagnetism returned in three-layer CrI3. The scientists will need to conduct further studies to understand why CrI3 displayed these remarkable layer-dependent magnetic phases.
The team wants to investigate the magnetic properties unique to 2-D magnets and heterostructures that contain a CrI3 monolayer or bilayer.