  We report on the possibility to detect hinge spin polarization in magnetic
topological insulators by resistance measurements. By implementing a
three-dimensional model of magnetic topological insulators into a
multi-terminal device with ferromagnetic contacts near the top surface, local
spin features of the chiral edge modes are unveiled. We find local spin
polarization at the hinges that inverts sign between top and bottom surfaces.
At the opposite edge, the topological state with inverted spin polarization
propagates in the reverse direction. Large resistance switch between forward
and backward propagating states is obtained, driven by the matching between the
spin polarized hinges and the ferromagnetic contacts. This feature is general
to the ferromagnetic, antiferromagnetic and canted-antiferromagnetic phases,
and enables the design of spin-sensitive devices, with the possibility of
reversing the hinge spin polarization of the currents.
