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TT: Fachverband Tiefe Temperaturen

TT 7: Matter at Low Temperature: Poster Session

TT 7.2: Poster

Montag, 25. Februar 2008, 14:00–18:00, Poster B

Measurements of amorphous and nanocrystalline ferromagnetic materials at low temperatures — •René Geithner, Alexander Steppke, Ralf Neubert, Wolfgang Vodel, and Paul Seidel — Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Helmholtzweg 5, 07743 Jena, Deutschland

For high-precision measurements of voltages and currents at low temperatures low-temperature superconducting DC SQUID sensors are successfully used in a wide range of applications. For an efficient coupling between the transducer and the readout DC SQUID superconducting transformers can be used. The transformer core should have a high relative permeability, even at temperatures below 4.2 K, to miniaturise the sensor. Additionally transfomers can directly be used to pickup electromagnetic fields, where the sensitivity is directly coupled to the core material. As the permeability of standard iron powder cores decreases rapidly for temperatures below 50 K we are investigating amorphous and nanocrystalline materials. We show first results of the permeability of Vitrovac, Vitroperm (VAC Hanau) and Nanoperm (Magnetec GmbH) over a wide temperature range from 300 K to 2 K. Measurements on the magnetic losses and associated noise figures are presented in respect to the permeability.