https://doi.org/10.1140/epjb/e2010-10636-4
Josephson coupling and Fiske dynamics in ferromagnetic tunnel junctions
1
Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner-Straße 8, 85748 Garching, Germany
2
Physik-Department, Technische Universität München, James-Franck-Straße, 85748 Garching, Germany
Corresponding author: a Achim.Marx@wmi.badw.de
Received:
19
August
2010
Published online:
15
December
2010
We report on the fabrication of Nb/AlOx/Pd0.82Ni0.18/Nb
superconductor/insulator/ferromagnetic metal/superconductor (SIFS) Josephson junctions with high
critical current densities, large normal resistance times area products, high quality factors, and
very good spatial uniformity. For these junctions a transition from 0- to π-coupling is observed
for a thickness dF 6 nm of the ferromagnetic Pd0.82Ni0.18 interlayer.
The magnetic field dependence of the π-coupled junctions demonstrates good spatial homogeneity
of the tunneling barrier and ferromagnetic interlayer. Magnetic characterization shows that the Pd0.82Ni0.18 has an out-of-plane anisotropy and large saturation magnetization, indicating
negligible dead layers at the interfaces. A careful analysis of Fiske modes provides information on
the junction quality factor and the relevant damping mechanisms up to about 400 GHz. Whereas losses
due to quasiparticle tunneling dominate at low frequencies, the damping is dominated by the finite
surface resistance of the junction electrodes at high frequencies. High quality factors of up to 30
around 200 GHz have been achieved. Our analysis shows that the fabricated junctions are promising
for applications in superconducting quantum circuits or quantum tunneling experiments.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010