One sample consisted essentially of a single thin layer of ferromagnetic nickel. By contrast, a second sample of this same nickel material was coated with a non-magnetic layer of gold.
Only a mere 30 nanometers (10-9 m) thick, the gold layer swallowed up the lion's share of the laser light so that barely any light ended up reaching the nickel layer. In spite of this, the nickel layer's magnetization rapidly dissipated shortly after the laser pulse entered each sample. However, in the case of the gold-coated sample, the researchers recorded a split-second delay. The observations were based on measurements obtained using circularly polarized femtosecond x-ray pulses at BESSY II, Berlin's own electron storage ring, with the help of the femtoslicing beamline.
"This allowed us to demonstrate experimentally that during this process, it isn't the light itself that is responsible for the ultrafast demagnetization but rather hot electrons, which are generated by the laser pulse," explains Andrea Eschenlohr. Excited electrons are able to rapidly move across short distances - like the ultra-thin gold layer. In the process, they also deliver their magnetic moment (their "spin") to the ferromagnetic nickel layer, prompting the breakdown of the latter's magnetic order. "Actually, what we had hoped to see is how we might be able to influence the spin using the laser pulse," explains Dr. Christian Stamm, who heads the experiment. "The fact that we ended up being able to directly observe how these spins migrate was a complete surprise to everyone."
Laser pulses are thus one possibility to generate "spin currents" where the spin is transferred in place of an electric charge. This observation is relevant for spintronics research where scientists design new devices from magnetic layered systems, which perform calculations based on spins rather than electrons, enabling them to very quickly process and store information while at the same time saving energy.
Dr. Eschenlohr concluded her doctoral work at HZB, in the context of which she generated the results described above, in late 2012. As of January of this year, Dr. Eschenlohr is a scientific associate at University of Duisburg-Essen.
The paper "Ultrafast spin transport as key to femtosecond demagnetization" will be published on 27. January 2013, 18:00 London time (GMT), in Nature Materials with doi: 10.1038/nmat3546.
Dr. Andrea Eschenlohr | EurekAlert!
Additive manufacturing reflects fundamental metallurgical principles to create materials
18.01.2019 | University of Sheffield
Brilliant glow of paint-on semiconductors comes from ornate quantum physics
17.01.2019 | Georgia Institute of Technology
The scientific and political community alike stress the importance of German Antarctic research
Joint Press Release from the BMBF and AWI
The Antarctic is a frigid continent south of the Antarctic Circle, where researchers are the only inhabitants. Despite the hostile conditions, here the Alfred...
World first experiments on sensor that may revolutionise everything from medical devices to unmanned vehicles
The new sensor - capable of detecting vibrations of living cells - may revolutionise everything from medical devices to unmanned vehicles.
Dead and alive at the same time? Researchers at the Max Planck Institute of Quantum Optics have implemented Erwin Schrödinger’s paradoxical gedanken experiment employing an entangled atom-light state.
In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. The crucial element of this gedanken...
Cellulose obtained from wood has amazing material properties. Empa researchers are now equipping the biodegradable material with additional functionalities to produce implants for cartilage diseases using 3D printing.
It all starts with an ear. Empa researcher Michael Hausmann removes the object shaped like a human ear from the 3D printer and explains:
The phenomenon of so-called superlubricity is known, but so far the explanation at the atomic level has been missing: for example, how does extremely low friction occur in bearings? Researchers from the Fraunhofer Institutes IWM and IWS jointly deciphered a universal mechanism of superlubricity for certain diamond-like carbon layers in combination with organic lubricants. Based on this knowledge, it is now possible to formulate design rules for supra lubricating layer-lubricant combinations. The results are presented in an article in Nature Communications, volume 10.
One of the most important prerequisites for sustainable and environmentally friendly mobility is minimizing friction. Research and industry have been dedicated...
16.01.2019 | Event News
14.01.2019 | Event News
12.12.2018 | Event News
18.01.2019 | Materials Sciences
18.01.2019 | Life Sciences
18.01.2019 | Health and Medicine