Researchers at the Lawrence Berkeley National Laboratory have successfully demonstrated that two-dimensional (2D) layered crystals held together by van der Waal forces—these include graphene and molybdenum disulfide—can exhibit intrinsic ferromagnetism. Not only did the team demonstrate that it exists in these materials, but the researchers also demonstrated a high degree of control over that ferromagnetism. The discovery could have a profound impact for applications including magnetic sensors and the developing use of spintronics for encoding information.
In research described in the journal Nature, the Berkeley scientists worked with a 2D chalcogenide layered material called chromium germanium telluride (CGT), a layered ferromagnetic insulator that has garnered interest because of its potential in spintronic devices. While the material has been around in bulk form for decades, only recently has it been made into 2D flakes, joining the list of other van der Waals crystals.
The researchers used an optical technique known as the magneto-optic Kerr effect that involves the use of a scanning Kerr optical microscope to observe the material. This technique detects how the rotation of linearly polarized light is changed when it interacts with electron spins in the material. This made it possible to detect unambiguously that the magnetism was originating from the atomically thin materials.