  We report the first study of the micro-SQUID response of a molecular system
to electromagnetic radiation. The advantages of our micro-SQUID technique in
respect to pulsed electron paramagnetic resonance (EPR) techniques consist in
the possibility to perform time-resolved experiments (below 1 ns) on
submicrometer sizes samples (about 1000 spins) at low temperature (below 100
mK).
  Resonant photon absorption in the GHz range was observed via low temperature
micro-SQUID magnetization measurements of the spin ground state S = 1/2 of the
molecular complex V15. The line-width essentially results from intra-molecular
hyperfine interaction. The results point out that observing Rabi oscillations
in molecular nanomagnets requires well isolated low spin systems and high
radiation power. Our first results open the way for time-resolved observations
of quantum superposition of spin-up and spin-down states in SMMs.
