Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 30: Spinabh
ängige Transportph
änomene II

MA 30.2: Vortrag

Freitag, 28. März 2003, 11:00–11:15, HSZ/401

Degradation of CoFe / Cu multilayers — •Jörg Ebert, Mohammad Ghafari, Branko Stahl, and Horst Hahn — Technische Universität Darmstadt, Institut für Materialwissenschaft, Fachgebiet Dünne Schichten, Petersenstrasse 23, 64287 Darmstadt

Since the discovery of the Giant Magnetoresistance effect there has been great effort to utilize it for industrial applications. Among the discussed material systems there are antiferromagnetically coupled multilayers based on Co and Cu. Crucial aspects for the use are the reduction of undesirable hysteresis and the understanding of the changes of the properties due to elevated temperatures. To reduce the hysteresis Co is alloyed with Fe. The presence of Fe enables studying the local microstructure and magnetic ordering by Moessbauer spectroscopy and so gives the chance to reveal the origins of the annealing behavior of GMR systems. Representing a basic system a trilayer consisting of Cu / Fe / Cu was prepared by molecular beam epitaxy using 57Fe. Moessbauer spectra of as prepared as well as of annealed samples show the changes in the microstructure due to diffusion, grain growth, and interface smoothening. To link these observations to magnetoresistive properties multilayers of the type [Fe (1.5 nm) / Cu (x nm)]*20 (2.0 nm < x < 3.1 nm) were analyzed. The field dependence of the electrical resistivity was quantified, measurements of the magnetization curves were carried out with a SQUID magnetometer, and the development of crystallinity was investigated by X-ray diffraction.