Dresden 2006 – scientific programme
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TT: Tiefe Temperaturen
TT 1: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs
TT 1.6: Talk
Monday, March 27, 2006, 10:45–11:00, HSZ 02
From 0 to π coupled Josephson junctions — •Martin Weides1, Hermann Kohlstedt1,2, Edward Goldobin3, Dieter Koelle3, and Reinhold Kleiner3 — 1Institute for Solid State Research, Research Centre Juelich, Germany — 2Department of Material Science and Department of Physics, University of Berkeley, USA — 3Physikalisches Institut - Experimentalphysik II, Universität Tübingen
We report on the successful fabrication of low-
TC SINFS Josephson junctions with 0 to π coupling
transition as a function of dF. Diluted ferromagnetic
Ni60Cu40 is used as F-interlayer. Our technology [1]
enables us to fabricate high quality junctions with low parameter
spread. We studied [2] the dependence of Ic and βC on
the thickness of ferromagnet and on temperature for both coupling
regimes. The influence of magnetic dead layer is investigated.
High Ic ≃ 5 A/cm2 and Vc≃ 20 mV for the π coupled state [2] are measured. For
T below 3 K the π coupled SINFS junction gets
underdamped, indicating a rather weak Cooper pair breaking in the
ferromagnetic
layer.
At the 0-π boundary half-integer vortices (semifluxons) may
spontaneously appear. They are pinned at the 0-π-boundary and
may have two different polarities with flux Φ = ±Φ0/2.
The semifluxon represents the ground state of the system and
therefore is extremely stable [3].
A patterning process of
0-π coupled SIFS junctions for the investigation of
semifluxons was worked out and
first results will be shown.
[1] Weides et al., to appear in Physica C
[2] Weides et al., to be submitted.
[3] E. Goldobin et al., PRB 66 (2002), 67 (2003), 69 (2004)