Magnetotransport in Spinventil-Systemen mit amorphen magnetischen und supraleitenden Teilschichten
FacultiesFakultät für Naturwissenschaften
LicenseStandard (Fassung vom 03.05.2003)
[Fe/B] multilayers and ferromagnetic (FM)/superconducting (SC)/ ferromagnetic (FM) layers were prepared by laser ablation. In situ electronspectroscopies (UPS,XPS) of the Fe/B multilayers and monitoring the electrical resistance during layer growth showed the occurrence of interface reactions. These reactions results in amorphous Fe_xB_100-x phases, which are spatially restricted to reaction depth of less than 3 nm. The amorphicity of the reacted interlayers was unequivocally proven by additional high-resolution electron microscopy (HRTEM) and their characteristically changed magnetic properties. Homogeneous amorphous Fe_xB_100-x films can be obtained by reducing the individual Fe and B layer thicknesses to below the reaction depth. These amorphous Fe_xB_100-x layers were used to prepare spin valve systems, which showed a GMR-effect. The dependency on the stoichiometry of the amorphous layer is discussed. In the case of the FM/SC/FM (Co/Nb/Fe)- layers the resistance and magnetization behavior was anaylzed and related to their superconducting transition temperature T_c. As opposed to what is expected by proximity effect theory, T_c exhibited a minimum in case of an anti-parallel relative orientation of the magnetization of the two sandwiching FM layers. Though this result is consistent with the predictions of spin imbalance theory, experiments on exchange biased CoO/Co/Nb/Fe systems revealed strong T_c changes even for a fixed relative magnetization orientation of the FM layers pointing to stray fields rather than magnetization orientations as causing the observed T_c shifts. This idea is corroborated by measurements on Fe/Nb and Co/Nb bilayers, which clearly show Tc changes related to specific magnetic domain configurations with a T_c maximum in the magnetically saturated state of the FM layer. Complementary micro-magnetic simulations delivering also the magnitude of stray fields support the picture of influencing T_c by switching the domain configurations.
Subject HeadingsLaserablation [GND]