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MA: Fachverband Magnetismus

MA 32: Magnetic Thin Films III

MA 32.2: Vortrag

Donnerstag, 26. März 2009, 10:30–10:45, HSZ 403

On amorphous CuMnAl- and NiTiAl-alloys, precursors of Half-Heusler and Heusler systems — Jan Rauchhaupt and •Peter Häussler — Chemnitz University of Technology, Institute of Physics, 09107 Chemnitz

Liquid and amorphous phases are the precursors of any crystalline phase and hence of Half-Heusler- and Heusler-alloys too. They may be of high interest to understand the stability and the physical properties of these phases. Generally, we describe structural stabilization as a self-organized resonance effect between global subsystems as all the valence electrons as one and the forming static structure as another one, enhanced occasionally by e.g. hybridization or charge transfer.

We are able to prepare (in situ, at T=4 K, in high vacuum) thin films of amorphous ternary alloys of different concentrations of Al with an early, and a late transition metal. As a function of temperature and composition we measure the static structure, by means of electron diffraction, the resistivity, the Hall coefficients, the thermopower, as well as relative White Line-intensities. We report on amorphous CuMnAl- and NiTiAl-alloys and indeed observe resonance effects, causing electronic transport anomalies. We find these effects near concentrations where so-called Half-Heusler- and Heusler-alloys exist and are able to grow their crystalline form by annealing the amorphous thin films.