Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/23777
Title: Electrical transport study of lateral superconductor - Ferromagnet Hybrid Devices
Authors: SAIDUR RAHMAN BAKAUL
Keywords: Superconductivity, spin triplet supercurrent, crossed Andreev reflection, frozen flux, ferromagnetic disk, OOMMF
Issue Date: 22-Nov-2010
Source: SAIDUR RAHMAN BAKAUL (2010-11-22). Electrical transport study of lateral superconductor - Ferromagnet Hybrid Devices. ScholarBank@NUS Repository.
Abstract: The interplay between superconductivity and inhomogeneous magnetization can give rise to many interesting and new physical phenomena such as crossed Andreev reflection (CAR) and long range odd triplet supercurrent (LRTS) which are still not well understood by the research community. One of the most promising platforms to study these kinds of phenomena is lateral devices consisting junctions made of superconductor (SC) and rectangularly patterned ferromagnet (FM). The underlying reason is that the rectangularly patterned FM can be a source of domain walls which provide inhomogeneous magnetization right at the SC?FM interface. One of the central questions motivating this thesis is whether such kind of devices can be used to detect existence of CAR and LRTS. We performed magnetoresistance (MR) measurements and found that these kinds of phenomena indeed play a role to determine the electronic transport characteristics of SC ? inhomogeneous FM interface. In addition to this, we studied electrical transport characteristics of SC- FM disk- SC devices and the effect of FM disk?s magnetization reversal process on it. Here we show that the sensitivity of SC-FM interface?s transport characteristic to stray field can be used to probe magnetization reversal process in FM disk and detect places with inhomogeneous magnetization. By performing micromagnetic modeling of the FM disk and analyzing the MR characteristics of SC- FM disk- SC devices at below and above superconducting transition temperature (Tc) we have been able to point out the onset and annihilation field of the vortex core in FM disk. The formation of vortex state during magnetization reversal causes a dramatic reduction of the stray field distribution near the edge of the disk which produces a sudden rise in Andreev conductance of SC-FM interface at a temperature below Tc. This results in a sudden drop in MR which enables us to find out the vortex onset field from electronic transport data. Results from micromagnetic modeling and spin polarized BTK simulation are in good agreement with these experimental observations.
URI: http://scholarbank.nus.edu.sg/handle/10635/23777
Appears in Collections:Ph.D Theses (Open)

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