Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 22: Transport: Poster Session

TT 22.55: Poster

Wednesday, February 27, 2008, 14:00–18:00, Poster B

Quantum transport in ferromagnetic Permalloy wires and films — •Daniel Neumaier, Anton Vogl, and Dieter Weiss — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Regensburg, Germany

We investigated the transport properties of mesoscopic Permalloy wires and films at milikelvin temperatures. The samples have been fabricated using electron beam lithography and lift-off techniques.

In wires with a width of 40 nm, a thickness of 15 nm and a length of 140 nm and 340 nm we found mesoscopic conductance fluctuations, originating from the electrons wave nature. These fluctuations reveal a phase coherence length of approx. 200 nm at 20 mK and decrease rapidly with increasing temperature.

To search for weak localization we fabricated arrays of wires to suppress conductance fluctuations. The arrays consist of 4 wires in parallel with a length of 4 micron, a width of 20 nm and a thickness of 15 nm. Below 1 K the conductance of the wire array is decreasing with decreasing temperature without an influence of an applied magnetic field. This behaviour can be explained by electron-electron-interaction, a contribution due to weak localization could not be found. In extended films with a thickness of 15 nm also a conductance decrease due to electron-electron interaction and no contribution due to weak localization was observed.