Münster 1997 – wissenschaftliches Programm
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AM: Magnetismus
AM 19: Magnetowiderstand I
AM 19.1: Hauptvortrag
Donnerstag, 20. März 1997, 09:30–10:15, F4
Giant Magnetoresistance and Kondo Effect in Melt-spun Au-Co — •D. S. Geoghegan1,2, A. Hütten1, G. Schmitz3, K.-H. Müller1, and L. Schultz1 — 1Institut für Festkörper- und Werkstofforschung Dresden, Posfach 270016, 01171 Dresden — 2on leave of absence from: University of Western Australia, Nedlands WA 6907, Australia — 3Universität Göttingen, Hospitalstraße 3-7, 37073 Göttingen
The dependence of the magnetic and transport properties on microstructure of Au-Co alloys at compositions near the 3-D fcc percolation threshold for Co in Au prepared by single roller melt spinning and subsequent heat treatment is reported. This composition is close to the eutectic enabling the formation of multilayer-like lamellae structures [1]. The microstructure is determined by electron microscopy (both TEM and SEM) and the magnetic and transport properties are measured in fields up to 7 T and at temperatures between 5 K and 300 K. The evolution of the microstructure with time of heat treatment gives rise to a competition between a Kondo-like effect and giant magnetoresistance (GMR) which is interpreted as arising from the transfer of Co atoms within the ribbon among three types of Co locations. These locations are: (a) Co dissolved in the Au matrix, (b) Co lamellae within the grains, and (c) Co precipitates at the grain boundaries. The respective behaviours that result are: (a) Kondo-like, (b) GMR, and (c) magnetic hysteresis.
[1] A. Hütten et al., Scripta Metall. Mater. 33, 1647 (1995)