Employing cutting-edge ultrafast imaging techniques through various methods, scientists have revealed an extraordinary phenomenon: ultrafast mechanical motion intertwined with a magnetic state change in layered materials. This magnetic effect holds the potential for applications in nanodevices demanding precise and rapid motion control. Just as a regular metal paper clip adheres to a magnet due to its iron content, materials of this kind are categorized as ferromagnets. Over a century ago, physicists Albert Einstein and Wander de Haas conducted a remarkable experiment involving a ferromagnet. By suspending an iron cylinder from a wire and subjecting it to a magnetic field, they observed the cylinder's rotation upon reversing the magnetic field's direction.

Figure 1. Scrambled Spins Inducing Atomic Layer Shearing in Iron Phosphorus Trisulfide (FePS3). (Credit: Argonne National Laboratory)

Figure 1 shows the intriguing phenomenon of shearing atomic layers within layered iron phosphorus trisulfide (FePS3), driven by the scrambling of electron spins upon illumination by a light pulse. The left side illustrates the arrangement of ordered spins, while the right side depicts the transformation to scrambled spins. This transformative process reveals the dynamic interplay between electron spin manipulation and atomic layer movement.

Haidan Wen, a physicist from the U.S. Department of Energy's Argonne National Laboratory, described Einstein and de Haas's experiment as almost magical, demonstrating the ability to induce rotation in a cylinder without any direct contact.

Alfred Zong, a Miller Research Fellow at the University of California, Berkeley, further elaborated, highlighting how this experiment harnessed the microscopic property of electron spin to trigger a mechanical response in a macroscopic object like the cylinder.

In a recent publication in Nature magazine, a collaborative team of researchers from Argonne and other prominent institutions disclosed a similar yet distinct effect in an "anti"-ferromagnet. This discovery could hold significant implications for applications requiring ultra-precise and swift motion control, such as high-speed nanomotors for biomedical purposes like nanorobotic-assisted minimally invasive procedures.

The contrast between ferromagnets and antiferromagnets lies in the property of electron spin. While ferromagnets possess electron spins aligned predominantly in one direction, antiferromagnets exhibit alternating spins that cancel each other out, making them less responsive to magnetic field changes. The question posed by the researchers was whether electron spin could provoke a unique response in an antiferromagnet, akin to the cylinder rotation effect in the Einstein-de Haas experiment.

To address this inquiry, the team chose to work with iron phosphorus trisulfide (FePS3), an antiferromagnetic material organized in layered structures. Each layer comprised only a few atoms' thickness, and the weak interaction between these layers set FePS3 apart from traditional magnets.

Using a combination of ultrafast laser pulses and advanced probes, the team observed that these pulses disrupted the ordered orientation of electron spins within the material, leading to disordered spins and a consequential mechanical response. Notably, due to the weak interlayer interaction, individual layers were capable of sliding relative to one another.

This motion occurred at an astonishingly rapid pace, oscillating within 10 to 100 picoseconds—equivalent to one trillionth of a second. Such swift movement highlighted the unique nature of the electron spin and atomic motion interplay in this layered antiferromagnet.

The research harnessed cutting-edge facilities like SLAC National Accelerator Laboratory, MIT, and the Center for Nanoscale Materials (CNM), along with beamlines at the Advanced Photon Source (APS), to carry out meticulous measurements at atomic and picosecond scales.

By unearthing a connection between electron spin and atomic motion specific to the layered antiferromagnet's structure, the researchers envision the potential to manipulate this motion through magnetic field adjustments or subtle strains, thereby opening doors to innovative possibilities for nanoscale devices.

Source: Argonne National Laboratory

Cite this article:

Hana M (2023), The Secrets of Ultrafast Motion: A Closer Look at the Fascinating Discoveries in Layered Magnetic Materials, AnaTechmaz, pp.491