Scientists discover unusual ultrafast motion in layered magnetic materials

A metal paper clip being attracted to a magnet is a classic example of ferromagnetism. However, scientists have discovered a similar yet distinct effect in an “anti”-ferromagnet, which has potential applications in ultra-precise and ultrafast motion control for devices like high-speed nanomotors used in biomedical applications such as nanorobots for minimally invasive surgery.

The difference between ferromagnets and antiferromagnets lies in the property of electron spin, which can have a direction represented by an arrow pointing up or down. In ferromagnets, all the electron spins can align in the same direction, resulting in a response to changes in the magnetic field. In antiferromagnets, the electron spins alternate between up and down, canceling each other’s effects and not responding to magnetic field changes in the same way as ferromagnets.

Researchers from Argonne National Laboratory, along with other national laboratories and universities, conducted experiments on a layered antiferromagnet called iron phosphorus trisulfide (FePS₃). They used ultrafast laser pulses to scramble the ordered spin orientation of electrons, leading to a mechanical response across the material. This response resulted in the shearing of atomic layers within FePS₃. The motion observed was incredibly fast, with oscillations occurring every 10 to 100 picoseconds.

The team used advanced scientific facilities to analyze the atomic structures and measure the material properties. These facilities included the ultrafast electron diffraction facilities at SLAC National Accelerator Laboratory and MIT, as well as the electron microscope facility in the Center for Nanoscale Materials and the beamlines at the Advanced Photon Source. The experiments revealed a unique link between electron spin and atomic motion in the layered antiferromagnet, opening up possibilities for controlling motion at the nanoscale.