  In this paper, we use the Hertz vector potential to define the
electromagnetic vector of different structured wavefields, and analyze the spin
properties of the wavefields. We show that for the single evanescent waves, the
total spin provides by the transverse spin and originates from the spatial
inhomogeneity of the momentum density of the field. However, for non-single
evanescent wave, there may be a part of the extraordinary spin component sE,
and the direction of sE is also perpendicular to the wave propagation
direction. In other words, it is transverse, but it does not originate from the
curl of the wave field momentum density. In addition, we also calculate the
spins of non-planar propagating waves, and analyze the spin characteristics of
these wave fields.
