  In this paper, we show the relation between the time-varying spinning nature
of the instantaneous Poynting vector and the phasor form of the complex
Poynting vector in the bulk of the gyromagnetic medium. We show the presence of
a transverse reactive power component in the bulk of the gyrotropic medium,
even for plane wave propagation. We use a simple quantification technique of
Poynting vector spin to analyze the rotation of the instantaneous Poynting
vector using the complex phasor form of the time-averaged Poynting vector. For
a transverse electric mode, we show the similarity between the Poynting vector
spin and the photonic spin of the magnetic field. The Poynting vector spin is
then used to represent the transverse power transfer across a ferrite-air
interface supporting TE surface wave modes. Considering a gyromagnetic
ferrite-filled rectangular waveguide following the TE mode profile, we show the
correspondence between the Poynting vector spin and the overall positive and
backward power flow. We analytically propose a mechanism to engineer the region
of the waveguide supporting backward and forward power propagation.
