日時：２０１１年２月７日 １４：４０-１６：１０
場所：A棟３０４号室

Title: Spintronics at the nano scale

Abstract:
Spintronics has had a large impact on our modern life style, especially regarding nonvolatile information storage. To further increase data rates and capacities in the coming decades, the special extend of the information units, i.e. the bits, need to be shrunk to nanometer size.

While it is possible with todays technology to create magnetically stable structures on this size, it is not possible to write information into the bits using magnetic fields. We show that using simple iron as magnetic material, information can be written on the scale of nm  using the electric field of a scanning tunneling microscope (STM) instead. This magneto-electric coupling is induced by the screening charges at the very surface of Fe which trigger a transition between the ferromagnetic and antiferromagnetic state [1].

Similarly, the reading process of the magnetic information, currently done by tunneling magnetoresistance (TMR) devices poses problems with extreme downscaling. In TMR junctions, transport of electrons across the junction proceeds by tunneling and the resistance of nm scale junctions become too large for high speed applications. All metallic giant magnetoresistance (GMR) junctions, however, have a so small resistance, that most of the voltage drop arises in the metallic leads reducing the GMR to only few percent.

We show that using single hydrogenphthalocyanine organic molecules as junctions in an STM geometry, the properties of TMR and GMR junctions can be combined reaching high magnetoresistance of 60% in combination with a low resistance area product for high speed operation [2].

[1] L. Gerhard et al., Nature Nanotechnology 2010

[2] S. Schmaus et al. Nature Nanotechnology 2011