Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 35: Focused Session: Charge and Spin Transport through Junctions at the Nanometre Scale

TT 35.4: Topical Talk

Donnerstag, 29. März 2012, 11:40–12:20, H 0104

Spin transport through organic molecules — •Wulf Wulfhekel — Physikalisches Institut, Karlsruhe Institute of Technology, Germany

We demonstrate that with the help of spin-polarized Scanning Tunneling Microscopy the spin transport across single organic molecules can be investigated and a molecular GMR junction can be realized. For this, single hydrogen phthalocyanine molecules were contacted by two ferromagnetic electrodes, i.e. a magnetic substrate and a magnetic STM tip. As substrate, ferromagnetic Co nano-islands grown Cu(111) were used, onto which the molecules were deposited. The magnetic state of the islands was determined by spin-polarized Scanning Tunneling Spectroscopy (STS) with Co tips. Then, the tip of the STM was approached in a controlled way towards a single molecule to contact the molecule. Below 0.4 nm distance, an attractive interaction between the tip and the molecule leads to a jump to contact of one of the side groups of the molecule, leading to a well defined molecular junction. Through the contacted molecule a GMR of 60% was observed which is one order of magnitude larger than the magnetoresistance without the molecule. This is explained on basis of ab initio calculations showing a selective hybridization of the molecular states with minority states of the electrodes. Finally, one of the electrodes has been replaced by an antiferromagnet forming an ideally hard magnetic layer. Due to the local character of the hybridization with the molecular states, a significant magnetoresistance can also be observed.