DC nanoSQUID from Nb thin films

We have prepared Nb thin film (thickness 80-100 nm) nanoSQUID with two symmetrically placed nanosized constrictions in superconducting loop. The nanoSQUID was prepared in two steps: at first a microsized SQUID was prepared and in the second step nanosized constrictions of the width of 120 nm in the SQUID loop were created by a focused ion beam technique. We studied the electrical and magnetic properties. From the obtained results, SQUID and constriction dimensions, the spin sensitivity was estimated to be about 50 μ_{B} Hz^{-1/2}. Further improvement of spin sensitivity is possible by lowering the SQUID and constriction dimensions.