MSc.Thesis Defense:Ege Aygıt

FABRICATION AND CHARACTERIZATION OF
SUPERCONDUCTING CIRCUITS CONSISTING OF MAGNETIC
JOSEPHSON JUNCTIONS

Ege AYGIT
Physics, MSc. Thesis, 2024

Thesis Jury

Asst. Prof. Yılmaz Şimşek  (Thesis Supervisor),
Prof. Özhan Özatay,

Prof. İsmet İnönü Kaya

Date & Time: 22nd, July 2024 –  3:00 PM

Place: FENS L035

Keywords : iron-oxide, ferromagnetic insulator, spintronics, quantum computing

Abstract

In the field of superconducting electronics, particularly for memory and information applications, the integration of magnetic Josephson junctions (MJJ) represents a significant advancement. The coexistence of superconductivity and magnetism at the superconductor/ferromagnet (S/F) interface offers various fascinating physical phenomena, thereby providing a promising basis for innovations in superconducting spintronics and quantum computing. The conventional S/F/S structure is realized by either sandwiching a ferromagnetic metal between two superconducting electrodes or by diluting the ferromagnetic alloy. However, low range voltage gap, extensive dissipation due to the metallic tunneling barrier and low coherence length, are present challenges in realizing superconducting devices consisting of MJJs. Theoretical studies have envisioned that ferromagnetic insulator (FI) based Josephson junctions would be promising candidates to overcome these challenges. This study focuses on investigating the effects of incorporating MJJs into superconducting circuits. Our experimental research, aimed at developing S/FI/S junctions, employed electron-beam lithography (EBL) and magnetron sputtering techniques with pure niobium (Nb) and magnetite (Fe3O4) targets. Utilizing high vacuum chambers and nano-scale lithography for controlled and precise fabrication, a procedure for the heterostructure of Nb/Fe-O/Nb junctions is established. This work expands the empirical findings and presents the practical potential of MJJs by overcoming the experimental challenges that have limited their development. By providing a deeper demonstration of the rich physics of S/FI/S junctions, we have paved the way for further experimental and theoretical exploration.