Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 19: Poster I (Bio- and Molecular Magnetism/ Magnetic Particles and Clusters/ Micro- and Nanostructured Magnetic Materials/ Magnetic Materials/ Multiferroics/ Magnetic Shape Memory Alloys/ Electron Theory of Magntism/ Spincaloric Transport/ Magnetic Coupling and Exchange Bias/ Magnetization Dynamics/ Micromagnetism and Computational Magnetics)

MA 19.72: Poster

Dienstag, 15. März 2011, 10:45–13:00, P2

About the 3ω method - the question current source or voltage source, plus application for field-dependent thermal conductivity measurements — •Johannes Kimling, Johannes Gooth, and Kornelius Nielsch — Institute of Applied Physics, University of Hamburg, Germany

The 3ω method is a standard method for thermal conductivity measurements. Researchers employ current-driven and voltage-driven setups, with or without common-mode subtraction for detecting the third harmonic component of the measurement signal. Nevertheless, there is a lack of clarity for which voltage-driven setups one has to consider a correction factor, as the formalism assumes an ideal current source at 1ω. In this work we show that for voltage-driven setups using common-mode subtraction, the application of a correction factor would be incorrect. On the other hand, for 3ω setups that use simple voltage-driven series circuits without common-mode subtraction a correction factor has to be considered. We employed the 3ω method to perform field-dependent thermal conductivity measurements on individual electrochemically synthesized nickel wires with diameters between 150 nm and 350 nm. Such structures exhibit anisotropic magnetoresistance. The field-dependent 3ω measurement allows observing the thermal analog: the anisotropic magnetothermal resistance. Measuring both effects simultaneously reveals spin-dependent changes in the Lorenz-number. Application to magnetic multilayer nanowires will allow studying the giant magnetothermal resistance in the cross-plane direction.