  In this work, we introduce a concept to enable dynamic beamforming of
terahertz (THz) wavefronts using applied magnetic fields (B). The proposed
system exploits the magnetically switchable hyperbolic dispersion of the InSb
semiconductor. This phenomenology, combined with diffractive surfaces and
magnetic tilting of scattered fields, allows the design of a metasurface that
works with either circularly or linearly polarized wavefronts. In particular,
we demonstrate numerically that the transmitted beam tilting can be manipulated
with the direction and magnitude of B. Numerical results, obtained through the
finite element method (FEM), are qualitatively supported by semi-analytical
results from the generalized dipole theory. Motivated by potential applications
in future Tera-WiFi active links, a proof of concept is conducted for the
working frequency f = 300 GHz. The results indicate that the transmitted field
can be actively tuned to point in five different directions with beamforming of
45{\deg}, depending on the magnitude and direction of B. In addition to
magnetic beamforming, we also demonstrate that our proposal exhibits magnetic
circular dichroism (MCD), which can also find applications in magnetically
tunable THz isolators for one-way transmission/reflection.
