  Spin-polarized scanning tunneling microscopy is identified as a suitable
experimental technique to investigate the quantitative quality of Lieb-Robinson
bounds on the signal velocity. The latest, most general bound is simplified and
it is shown that there is a discrepancy by a factor of approximately 4 between
the corresponding limit speed and some estimated exact velocities in atomic
spin chains. The observed discrepancy facilitates conclusions for a further
mathematical improvement of Lieb-Robinson bounds. The real signal propagation
can be modified with several experimental parameters from which the bounds are
independent. This enables the application of Lieb-Robinson bounds as upper
limits on the enhancement of the real signal speed for information transport in
spintronic devices.
