| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 94 === Abstract
The magnetic tunnel junctions (MTJs) are consisted of ferromagnet/insulator/ferromagnet (FM/I/FM). Tunnel magnetoresistance (TMR) is strongly influenced by the electronic and magnetic properties at the FM/I interface. Considering the proximity effect in ferromagnet/superconductor (FM/SC), we sputtered Nb on the top FM layer of pseudo spin-valve (PSV) magnetic tunnel junctions to observe how the superconducting Nb influences the FM layer. With the help of the contrast experiment, we find that the resistance of the antiparallel state maybe influenced by Nb and it becomes lower below the superconducting transition temperature (Tc). However, the resistance in paralleled state is not significantly influenced by Nb, resulting in the decrease of TMR values.
In the thickness dependence of Nb, we find that TMR is not apparently influenced in SC state as the thickness of Nb is below 100 nm. Comparing with that in the case of 500 nm Nb thickness, the TMR value shows retarding decrease as cooling through Tc for those of Nb thickness between 150 nm and 250 nm.
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