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TT: Fachverband Tiefe Temperaturen

TT 17: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs

TT 17.4: Vortrag

Montag, 31. März 2014, 15:45–16:00, HSZ 201

Hybrid superconducting magnetic tunnel junctions: Coexistence of TMR and Josephson effects — •Ondrej Vavra^{1, 2}, Rohit Soni², Nico Ruppelt², Adrian Petraru², Hermann Kohlstedt², and Christoph Strunk¹ — ¹Institute for Experimental and Applied Physics, University of Regensburg, D-93040 Regensburg, Germany — ²Nanoelektronik, Technical Faculty, University of Kiel, D-24143 Kiel, Germany

We report on the latest results observed on hybrid superconducting SFIFS Josephson junctions with ferromagnet thickness-wedge (F). The Nb-Fe-Al₂O₃-Fe-Nb junctions were deposited by means of dc-magnetron sputtering technique. Junctions exhibit both Josephson effect and tunneling magnetoresistance (TMR) effect. Fraunhofer magnetic field dependence of the critical current I_C(B) proves the homogeneity of the barrier over the 4 inch wafer. The properties of the junctions such as I_C, normal conductance G_n and the tunneling magnetoresistance (TMR), respectively, strongly dependent on the oxidation parameters of the barrier (Al2O3). The different thickness of intermediate Al gives rise to the over- or under-oxidation, resulting in the Nb-Fe-Fe*-Al₂O₃-Fe-Nb or the Nb-Fe-Al-Al₂O₃-Fe-Nb, respectively. The layers denoted as Fe* (by oxygen affected Fe) and Al (residual Al layer underlying the Al₂O₃) are considered as parasitic since they suppress TMR. The impact of different thickness of both ferromagnetic layers d_F on density of states, TMR and Josephson effect will be presented too.