Shrinking iron films strengthens laser-driven demagnetization

Shrinking iron films strengthens laser-driven demagnetization Lisa Lock Scientific Editor Robert Egan Senior Editor From photos and videos to documents, vast amounts of data are stored on hard drives in large data centers. These devices use tiny magnetic regions whose orientation determines the information stored. But how could data be stored even faster in the future? One possible approach involves ultrashort laser pulses, which can alter the magnetic order of materials in an extremely short time. A team from Collaborative Research Center 1242 at the University of Duisburg-Essen (UDE), working with Helmholtz-Zentrum Berlin, has therefore investigated how the thickness of an iron film affects its so-called ultrafast demagnetization. During this process, a laser pulse causes the material to lose part of its magnetic order within an extremely short period of time. The result: The thinner the iron layer, the stronger the effect. At a thickness of just 2 nanometers—equivalent to two millionths of a millimeter—demagnetization was approximately 75% stronger than in a 16-nanometer-thick layer, even though the intensity of the laser excitation remained the same. These findings are published in the journal Advanced Science. But why do thinner layers respond more strongly? The key lies in electron spins, whose collective alignment is responsible for the magnetism of iron. "In particularly thin iron layers, a larger proportion of these spins are located at the material's interfaces. There, they have fewer neighboring spins with which they can interact magnetically," explains Dr. Andrea Eschenlohr from the Faculty of Physics. "Put simply, the spins have fewer neighbors to hold on to. This makes it easier for a laser pulse to disrupt their magnetic order." Researchers had already suspected that the thickness of an iron layer could influence demagnetization. What came as a surprise, however, was the magnitude of the effect and the fact that it stems from the material's magnetic properties—rather than differences in light absorption or vibrations of the atomic lattice. In the long term, the findings could contribute to the development of magnetic storage media in which information is written using ultrashort laser pulses. However, several challenges still need to be overcome before the technology can be put into practice. For example, suitable laser sources would need to be integrated into electronic devices, and it would have to be possible to target extremely small areas precisely in order to achieve high storage densities. Publication details Yoav William Windsor et al., Nanoscale Confinement Enhances Ultrafast Demagnetization, Advanced Science (2026). DOI: 10.1002/advs.77058 Journal information: Advanced Science Provided by University of Duisburg-Essen