We measured the magnetic field dependence of the critical current of high quality Nb-based planar Josephson tunnel junctions in the presence of a controllable non-uniform field distribution. We found skewed and slowly changing magnetic diffraction patterns quite dissimilar from the Fraunhofer-like ones typical of a homogeneous field. Our findings can be well interpreted in terms of recent theoretical predictions [R. Monaco, J. Appl. Phys. vol.108, 033906 (2010)] for a uniform magnetic field gradient leading to Fresnel-like magnetic diffraction patterns. We also show that Fiske resonances can be suppressed by an asymmetric magnetic field profile.
@article{arxiv.1101.1610,
title = {Josephson Tunnel Junctions in a Magnetic Field Gradient},
author = {Roberto Monaco and Jesper Mygind and Valery Koshelets},
journal= {arXiv preprint arXiv:1101.1610},
year = {2015}
}