Investigation and control of motion of magnetic vortices in the thin superconducting YBa2Cu3O7-x films

Lina Steponavičienė

Doctoral dissertation

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The present thesis explores superconducting YBa2Cu3O7-x thin films containing laser-formed regions of weak superconductivity. The object of the research is the mixed-state type-II superconductor YBa2Cu3O7-x. The aim of this work is to study and explain the electrical and magnetic properties of mixedstate, dc-biased superconducting devices with currents exceeding the critical current of the superconductor at T < Tc of the superconducting material. The PhD thesis focuses on the following objectives: to fabricate superconducting YBa2Cu3O7-x devices containing regions of weak superconductivity by means of laser-pattering/writing technique out of the YBa2Cu3O7-x thin superconducting films manufactured by MOCVD method. To study electric and magnetic properties of these devices biased with direct current which strength is greater than the critical current of the superconducting material and based on analysis of experimentally estimated electric losses to explain the conditions under which the mixed-state in the material appears and how it develops. The main purpose of this research is to find a way how to predict and control randomly appearance and motion of Abrikosov magnetic vortices in the mixed-state superconducting devices.

The dissertation comprises an introduction, three chapters, conclusions, the cited references, and the author's scientific publications on the subject.

The introductory chapter includes the research problem and the significance of the study on the thesis, the object of research, the aims and objectives, the prevailing research methodology, its scientific novelty, the practical significance of the examined results, and the defended statements.

The first chapter is devoted to literature review.

The second chapter describes the superconducting thin films growing and research techniques.

The third chapter endows with the results achieved after the exploration of YBa2Cu3O7-x layers and devices. This chapter provides evidence that the magnetic field the penetrates via the areas of weak superconductivity in the superconductor YBa2Cu3O7-x by means of Abrikosov magnetic vortices. This chapter shows how we can control coherent motion in YBa2Cu3O7-x superconductors, in the areas of weak superconductivity, by means of Abrikosov magnetic vortices.

The main findings were discussed at eleven scientific conferences. The main research results are presented in five scientific publications.

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Imprint No:
145×205 mm
86 p.
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