Tuesday, April 30, 2013

1304.7584 (Roman Wölbing et al.)

Nb nano superconducting quantum interference devices with high spin
sensitivity for operation in magnetic fields up to 0.5\,T

Roman Wölbing, Joachim Nagel, Tobias Schwarz, Oliver Kieler, Thomas Weimann, Johannes Kohlmann, Alexander Zorin, Matthias Kemmler, Reinhold Kleiner, Dieter Koelle
We investigate electric transport and noise properties of microstrip-type submicron direct current superconducting quantum interference devices (dc SQUIDs) based on Nb thin films and overdamped Josephson junctions with a HfTi barrier. The SQUIDs were designed for optimal spin sensitivity $S_\mu^{1/2}$ upon operation in intermediate magnetic fields $B$ (tens of mT), applied perpendicular to the substrate plane. Our so far best SQUID can be continuously operated in fields up to $B\approx\pm50\,\rm{mT}$ with rms flux noise $S_{\Phi,\rm w}^{1/2}\leq250\,\rm{n\Phi_0/Hz^{1/2}}$ in the white noise regime and spin sensitivity $S_{\mu}^{1/2}\leq29\,\rm{\mu_B/Hz^{1/2}}$. Furthermore, we demonstrate operation in $B=0.5\,\rm{T}$ with high sensitivity in flux $S_{\Phi,\rm w}^{1/2}\approx680\,\rm{n\Phi_0/Hz^{1/2}}$ and in electron spin $S_{\mu}^{1/2}\approx79\,\rm{\mu_B/Hz^{1/2}}$. We discuss strategies to further improve the nanoSQUID performance.
View original: http://arxiv.org/abs/1304.7584

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