Shot noise and magnetism of Pt atomic chains: accumulation of points at   the boundary
  Pt is known to show spontaneous formation of monatomic chains upon breaking a metallic contact. From model calculations, these chains are expected to be spin polarized. However, direct experimental evidence for or against magnetism is lacking. Here, we investigate shot noise as a potential source of information on the magnetic state of Pt atomic chains. We observe a remarkable structure in the distribution of measured shot-noise levels, where the data appear to be confined to the region of nonmagnetic states. While this suggests a nonmagnetic ground state for the Pt atomic chains, from calculations we find that the magnetism in Pt chains is due to 'actor' electron channels, which contribute very little to ballistic conductance and noise. On the other hand, there are weakly polarized 'spectator' channels, which carry most of the current and are only slightly modified by the magnetic state. 
Manohar Kumar, Oren Tal, Roel H. M. Smit, Alexander Smogunov, Erio   Tosatti, and Jan M. van Ruitenbeek
cond-mat.mes-hall