Der Einfluß der Grenzflächenrauhigkeit auf den Riesenmagnetowiderstandseffekt in epitaktischen Fe/Cr/Fe-Schichten

Abstract

Epitaxial Fe/Cr/Fe trilayers with varying interface roughness were fabricated using molecular beam epitaxy. They were patterned into stripes to investigate the influence of interface roughness on the giant magnetoresistance (GMR) effect. (001) oriented gold and silver buffer layers on GaAs were used as suhstrates and proved to be a very good choice for monocrystalline growth. During layer growth, single deposited monolayers could be distinguished observing oscillating intensities of the diffraction pattern of high energy electrons (RHEED). This feature was exploited to determine layer thicknesses and to intentionally finish the preparation of a given layer at filled or half filled top atomie layers, corresponding to flauer or rougher surfaces, respectively. An essential condition for the observation of GMR behaviour is the possibility to influence the magnetic configuration of the sample. This was given, for the magnetizations of the iron layers separated by the chromium spacer layer of a suitable thickness were coupled antiferromagnetically and could be aligned parallel by an external magnetic field. In spite of the dominating electrical conductivity of the underlying gold or silver buffer layer, measuring the giant magnetoresistance with the current flowing in the plane of the layers (CIP geometry) revealed possible. In samples with interface roughnesses tailored during preparation, the amplitude of the GMR effect depended on the roughnesses of the interfaces of the fron and chromium layers: With rougher interfaces, the GMR effect was enhanced. In this work, the influence of the interfaces on the GMR effect was examined using well-defined monocrystalline samples with the simplest possible configuration, i. e. trilayers made of two ferromagnetic layers separated by one spacer layer. In former approaches to investigate the rote of the interfaces, multilayered samples (some of them polycrystalline) were used or the interfaces were modified introducing other materials