  Pt is known to show spontaneous formation of chains of metal atoms upon
breaking a metallic contact. From model calculations these have been predicted
to be spin polarized, which is reasonable in view of the Stoner enhanced
susceptibility of bulk Pt and the increased density of states due to the
reduced dimensionality. Here, we demonstrate that shot noise reveals
information on the magnetic state of Pt atomic chains. Against all predictions,
we find clear evidence for a non-magnetic ground state for the conductance
channels of Pt atomic chains.
