  Reading and manipulating the spin status of single magnetic molecules is of
paramount importance both for applicative and fundamental purposes. The
possibility to combine Electron Spin Resonance (ESR) and Scanning Tunnelling
Microscopy (STM) has been explored one decade ago. A few experiments have
raised the question whether or not an EPR spectrum of single molecule is
detachable. Only a few data have been reported in modern surface science
literature. To date it has yet to be proven to which extent ESR can be reliably
and reproducibly performed on single molecules. We are setting up a new ESR-STM
(spectrometer) to verify and study the effect of spin-spin correlations in the
frequency spectrum of the tunneling current which flows through a single
magnetic adsorbate and a metal surface. Here we discuss, the major experimental
challenges that we are attempting to overcome.
