Switching Magnetism on the Spot

Science  14 Sep 2007:
Vol. 317, Issue 5844, pp. 1465a
DOI: 10.1126/science.317.5844.1465a
CREDIT: STEFAN KRAUSE/UNIVERSITY OF HAMBURG

In magnetic hard drives, information is typically written by application of a magnetic field, and readout is performed with a separate electrical probe. The bit densities that can be achieved this way are limited by stray magnetic fields that can affect nearby bits and possibly destroy information that was already stored. The use of spin-polarized current to locally control and read out the magnetization is expected to overcome such problems, but the underlying mechanisms involved in spin-polarized magnetization switching remain unclear. Krause et al. (p. 1537) show that spin-polarized current from a scanning tunneling microscope tip can be used to both manipulate and read out the magnetization in small islands of iron atoms. The magnetization switching in the island is dominated by a spin-torque effect exerted by the spin-polarized current, whereas the Oersted field (magnetic field arising from current flow) is small.

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