  Although there are several proposals of relativistic spin in the literature,
the recognition of intrinsicality as a key characteristic for the definition of
this concept is responsible for selecting a single tensor operator that
adequately describes such a quantity. This intrinsic definition does not
correspond to Wigner's spin operator, which is the definition that is widely
adopted in the relativistic quantum information theory literature. Here, the
differences between the predictions obtained considering the intrinsic spin and
Wigner's spin are investigated. The measurements involving the intrinsic spin
are modeled by means of the interaction with an electromagnetic field in a
relativistic Stern-Gerlach setup.
