  Vector spin chirality is one of the fundamental characteristics of complex
magnets. For a one-dimensional spin-spiral state it can be interpreted as the
handedness, or rotational sense of the spiral. Here, using spin-polarized
scanning tunneling microscopy, we demonstrate the occurrence of an atomic-scale
spin-spiral in finite individual bi-atomic Fe chains on the (5x1)-Ir(001)
surface. We show that the broken inversion symmetry at the surface promotes one
direction of the vector spin chirality, leading to a unique rotational sense of
the spiral in all chains. Correspondingly, changes in the spin direction of one
chain end can be probed tens of nanometers away, suggesting a new way of
transmitting information about the state of magnetic objects on the nanoscale.
