| Summary: | 碩士 === 輔仁大學 === 物理學系 === 89 === Since the discovery of Giant Magnetoresistance (GMR) in Fe/Cr multilayers, there is theoretical prediction that magnetic coupling can be found across super-conducting layers. Another related topic was p phase between superconductor across ferromagnetic films. When ferromagnetic film has certain thickness, a phase difference p state was found to have lower energy than a usual state with zero phase difference.
Nb/Co multilayers were grown on Si (100) substrates at room temperature by dc sputtering method. We measured the temperature dependence of super-conducting upper critical fields (Hc2) to find out whether coupling between su-perconductors can occur across ferromagnet, and whether there is oscillation of transition temperature in superconductor / ferromagnet multilayers with in-creasing ferromagnetic layer thickness. In addition to measuring the Current In Plane (CIP) resistance, we measured the Current Perpendicular to Plane (CPP) resistance.
We found Hc2 crossovers from two-dimension (2D) non-linear behavior to three-dimension (3D) linear one. When Co thickness increases to 6A, Hc2 changes from 3D abrutly to 2D, indicating Co becomes ferromagnetically or-dered. When Nb thickness increases, crossover occurs gradually around 800A. We also present successful results on CPP resistance measurements.
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