  We examine the possibility of probing superconductivity effects in metal
nanoclusters via diamond magnetometry. Metal nanoclusters have been proposed as
constitutive elements of high T$_c$ superconducting nanostructured materials.
Magnetometry based on the detection of spin-selective fluorescence of
nitrogen-vacancy (NV) centers in diamond is capable of nanoscale spatial
resolution and could be used as a tool for investigating the properties of
single or multiple clusters interacting among each other or with a surface. We
have carried out sensitivity estimates and experiments to understand how these
magnetometers could be used in such a situation. We studied the behavior of the
sensor as a function of temperature and detected the flux exclusion effect in a
superconductor by monitoring the [111]-orientation fine structure spectrum in
high-NV density diamond. Our results show that phase transitions can be
ascertained in a bulk superconductor with this technique while the principal
zero field splitting parameter ($D$) demonstrates a temperature dependence that
may require compensation schemes.
