Magneto-optical imaging of dendritic flux instability is reported for NbN films exposed to magnetic fields ramped at a fast rate (0.1-3.2 kT s-1). The results show that as the magnetic ramp rate increases, the temperature and field range of the instability extends significantly. In particular, the lower and upper threshold fields (H1 th and H2 th, respectively) that bound the field range for dendritic instability are affected. The upper field is found to increase linearly with the applied field sweep rate, a behavior which is discussed in terms of a recent theoretical work (Vestgarden et al 2016 Phys. Rev. B 73 174511). The extended instability range should be taken into account in applications in which the superconducting films are exposed to rapid changes in the magnetic field.
|Journal||Superconductor Science and Technology|
|State||Published - 6 Sep 2018|
Bibliographical noteFunding Information:
This work was supported by Israel Science Foundation (ISF-164/12). The authors thank Lior Shani for technical assistance with the MPMS measurements.
© 2018 IOP Publishing Ltd.
- dendritic flux instability
- magneto-optical imaging