Variable sample temperature scanning superconducting quantum interference device microscope

We demonstrate a design for a scanning superconducting quantum interference device (SQUID) microscope in which the sample temperature can be varied over a large range. In this design, both sample and SQUID are in the same vacuum space, separated by a few microns. By firmly anchoring the SQUID to a low-temperature bath, the sample temperature can be changed while the SQUID remains superconducting. This allows magnetic imaging at varying sample temperatures with micron-scale spatial resolution and the sensitivity of a low-$Tc$ SQUID. We demonstrate this approach by imaging the temperature dependence of Abrikosov vortices in thin films of the high-temperature superconductor $YBa2Cu3O7−δ.$ We extract the in-plane penetration depth $λab(T)$ in our samples from these measurements.