My watch list  

Antiferromagnetic dysprosium reveals magnetic switching with less energy



A short laser pulse pertubates magnetic order in dysprosium. This happens much faster if the sample had a antiferromagnetic order (left) compared to ferromagnetic order (right).

HZB scientists have identified a mechanism with which it may be possible to develop a form of magnetic storage that is faster and more energy-efficient. They compared how different forms of magnetic ordering in the rare-earth metal named dysprosium react to a short laser pulse. They discovered that the magnetic orientation can be altered much faster and with considerably less energy if the magnetic moments of the individual atoms do not all point in the same direction (ferromagnetism), but instead point are rotated against each other (anti-ferromagnetism).

Dysprosium is not only the atomic element with the strongest magnetic moments, but it also possesses another interesting property: its magnetic moments point either all the same direction (ferromagnetism) or are tilted against each other, depending on the temperature. This makes it possible to investigate in the very same sample how differently oriented magnetic moments behave when they are excited by an external energy pulse.

Magnetic-order perturbation examined at BESSY II

Physicist Dr. Nele Thielemann-Kuehn and her colleagues have now investigated this problem at BESSY II. The BESSY II X-ray source is one of the few facilities worldwide that enables processes as fast as magnetic-order perturbations to be observed. Her finding: the magnetic orientation in antiferromagnetic dysprosium can be much more easily toggled using a short laser pulse than in ferromagnetic dysprosium.

"This is because the magnetic moments at the atomic level are coupled to angular momenta like that of a gyroscope", explains Thielemann-Kuehn. Tipping a rotating gyroscope requires force because its angular momentum must be transferred to another body. "Albert Einstein and Wander Johannes de Haas showed in a famous experiment back in 1915 that when the magnetisation of a suspended bar of iron changes, the bar begins to rotate because the angular momenta of the atomic-level magnets in the suspended bar are transferred to it as a whole. If the atomic-level magnetic momenta are already pointing in different directions initially, their angular momenta can interact with one another and cancel each other out, just as if you were to combine two gyroscopes rotating in opposite direction", clarifies Dr. Christian Schuessler-Langeheine, head of the group.

Antiferromagnetic order is perturbed faster

The transfer of angular momentum takes time, though. Antiferromagnetic order, for which this transfer is not required, should therefore be able to be perturbed faster than ferromagnetic order. The empirical evidence for this conjecture has now been delivered in this study by Thielemann-Kuehn and her colleagues. Moreover, the team also discovered that the energy needed in the case of the antiferromagnetic momenta is considerably lower than in the case of ferromagnetic order.

From this observation, the scientists have been able to suggest how materials could be developed with a combination of ferromagnetic and antiferromagnetic aligned spins that are suitable as magnetic storage media and might be switched with considerably lower energy expenditure than material made from conventional magnets.

Facts, background information, dossiers
  • HZB
  • Bessy
  • ferromagnetism
  • storage devices
  • antiferromagnetism
  • ferromagnets
  • antiferromagnets
  • rare earth metals
More about Helmholtz-Zentrum Berlin für Materialien und Energie
More about Helmholtz-Gemeinschaft
  • News

    Charge transport in hybrid silicon solar cells

    The system they investigated is based on conventional n-type silicon wafers coated with the highly conductive polymer mixture PEDOT:PSS and displays a power conversion efficiency of about 14%. This combination of materials is currently extensively investigated by many teams in the research ... more

    Camera for the Nano-Cosmos

    To gain even deeper insights into the smallest of worlds, the thresholds of microscopy must be expanded further. Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the TU Dresden, in cooperation with the Freie Universität Berlin, have succeeded in combining two established me ... more

    Observation of the superheavy element 117

    The periodic table of the elements is to get crowded towards its heaviest members. Evidence for the artificial creation of element 117 has recently been obtained at the GSI Helmholtz Centre for Heavy Ion Research, an accelerator laboratory located in Darmstadt, Germany. The experiment was p ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE