Scanning superconducting quantum interference device on a tip for   magnetic imaging of nanoscale phenomena
  We describe a new type of scanning probe microscope based on a superconducting quantum interference device (SQUID) that resides on the apex of a sharp tip. The SQUID-on-tip is glued to a quartz tuning fork which allows scanning at a tip-sample separation of a few nm. The magnetic flux sensitivity of the SQUID is 1.8 {\mu}_0/Hz^{1/2} and the spatial resolution is about 200 nm, which can be further improved. This combination of high sensitivity, spatial resolution, bandwidth, and the very close proximity to the sample provides a powerful tool for study of dynamic magnetic phenomena on the nanoscale. The potential of the SQUID-on-tip microscope is demonstrated by imaging of the vortex lattice and of the local AC magnetic response in superconductors. 
A. Finkler, D. Vasyukov, Y. Segev, L. Ne'eman, E. O. Lachman, M. L.   Rappaport, Y. Myasoedov, E. Zeldov, and M. E. Huber
cond-mat.supr-con cond-mat.mes-hall