by Staff Writers
Bochum, Germany (SPX) Sep 14, 2011
Bochum's physicists led by Prof. Dr. Hartmut Zabel have demonstrated the spin pumping effect in magnetic layers for the first time experimentally. The behaviour of the spin pumping had previously only been predicted theoretically. The research team at the RUB has now succeeded in measuring the effect using ultrafast X-ray scattering with picosecond resolution.
Through their rotation of the magnetic moments, the so-called magnetic precession, single electrons can mutually influence each other's rotation (spin) through a non-magnetic intermediate layer. This is a crucial insight for future generations of magnetic sensors in hard disk read heads and other data storage. The researchers reported on their findings in Applied Physics Letters.
Magnetic spinning tops are different
"In particular, we do not expect that one spinning top can affect the rotation of the other", said Prof. Hartmut Zabel. Whether both tops rotate in the same or in the opposite direction, should have no impact on the number of rotations before they come to a stop. "But that's precisely what happens with magnetic spinning tops", as Bochum's research group confirmed in its experiments.
Magnetic rotation in the gigahertz range
However, once one of the two ferromagnetic layers is stimulated to a very fast precession in the gigahertz range, the damping of the precession depends of the orientation of the second magnetic layer. If both layers have the same orientation, then the damping is lower. If both are oriented in opposite directions, then the damping is higher.
In other words, ferromagnetic layers, which do not interact with each other statically because the intermediate layer is too thick, are still able to "affect" each other dynamically through pumping and diffusion of spins from one layer to another.
A typical "spin valve" in data storage
"Therefore, the finding that the damping of the magnetic precession is influenced by spin pumping through non-magnetic intermediate layers is not only of fundamental but also of practical interest for industrial applications" said Professor Zabel.
R. Salikhov,R. Abrudan, F. Brussing, St. Buschhorn, M. Ewerlin, D. Mishra, F. Radu, I. A. Garifullin, and H. Zabel, "Precessional Dynamics and Damping in Co/Cu/Py Spin Valves", Applied Physics Letters Vol. 99, page 092509 (2011), DOI: 10.1063/1.3633115
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Intel teams with Google on smartphone chips
San Francisco (AFP) Sept 13, 2011
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