Physicists at BESSY II observe ultrafast magnetic order collapse in spintronic bilayers within 300 femtoseconds

Physicists use femtoslicing at BESSY II to observe magnetic order collapse in bilayer systems, revealing secrets of ultrafast spintronic energy transfer.

By: AXL Media

Published: Apr 30, 2026, 9:08 AM EDT

Source: Information for this report was sourced from EurekAlert!

Breakthrough in Ultrafast Spintronic Dynamics

Researchers at the BESSY II X-ray source have achieved a new level of precision in observing the interaction between ferromagnetic and antiferromagnetic layers, the fundamental components of spintronic devices. Unlike traditional electronics that rely on moving charges, spintronics utilizes electron spins to process data, offering the potential for significantly higher speeds and reduced energy consumption. According to the research team, led by Wolfgang Kuch, the study successfully tracked how magnetic order changes in real-time following excitation by a short laser pulse. This level of atomic resolution on ultra-fast timescales is essential for advancing components toward the terahertz clock speeds required for future computing applications.

Femtoslicing snapshots at BESSY II

The experimental breakthroughs were made possible through a method known as femtoslicing, which allows scientists to take stroboscopic snapshots of a magnetic state within a few quadrillionths of a second. By employing X-ray magnetic dichroism at the Helmholtz-Zentrum Berlin facility, the researchers were able to separate the signals from each distinct layer in the bilayer system. The sample utilized in this experiment consisted of nine layers of ferromagnetic iron deposited over nine layers of antiferromagnetic cobalt oxide. This setup allowed the team to measure the reflected intensity of circularly and linearly polarized soft X-rays to see exactly how each material responded to external stimuli.

Simultaneous Collapse of Magnetic Order

The most striking finding of the study was that both magnetic orders collapsed nearly simultaneously within approximately 300 femtoseconds of being struck by an 800-nanometer laser pulse. Wolfgang Kuch noted that this result was unexpected because cobalt oxide is transparent at that specific wavelength and cannot absorb the laser pulse directly. The simultaneous collapse indicates that the antiferromagnetic layer does not react to the light itself, but rather to the excitation originating in the adjacent iron layer. This discovery shifts the understanding of how energy moves through these complex bilayer systems on an ultrafast scale.