Characterization of Lateral Junctions and Micro-SQUIDs Involving Magnetic Multilayers

We have fabricated and characterized at low temperatures Nb/Ni/(Al/Ni)
₁₄
/Nb lateral junctions and Nb micro-SQUIDs involving (Al/Py)
₁₀
multilayers (here Py is permalloy: 80% Ni − 20% Fe). We have studied
I
-
V
curves and Josephson critical current as a function of an external magnetic field (
I
_c
(
H
)) at various temperatures and orientations of the applied magnetic field. These studies revealed that, for some orientations of the externally applied magnetic field, the
I
_c
(
H
) dependence of the lateral junctions has a component highly sensitive to magnetic field. In addition, we have observed a SQUID-like
I
_c
(
H
) dependence for devices, in which an orthogonally oriented (with respect to the substrate) Nb loop that includes two nanoscopic Josephson junctions is filled with a (Al/Py)
₁₀
multilayer. We believe the devices presented here are promising as magnetic field sensors on nanoscale for various applications where high spatial resolution is required.