  We present a low-frequency, broadband polarization study of the FRII radio
galaxy PKS J0636-2036 (z = 0.0551), using the Murchison Widefield Array (MWA)
from 70 to 230 MHz. The northern and southern hotspots (separated by ~14.5' on
the sky) are resolved by the MWA (3'.3 resolution) and both are detected in
linear polarization across the full frequency range. A combination of Faraday
rotation measure (RM) synthesis and broadband polarization model-fitting are
used to constrain the Faraday depolarization properties of the source. For the
integrated southern hotspot emission, two RM component models are strongly
favoured over a single RM component, and the best-fitting model requires
Faraday dispersions of approximately 0.7 and 1.2 rad/m$^2$ (with a mean RM of
~50 rad/m$^2$). High resolution imaging at 5" with the ATCA shows significant
sub-structure in the southern hotspot and highlights some of the limitations in
the polarization modelling of the MWA data. Based on the observed
depolarization, combined with extrapolations of gas density scaling-relations
for group environments, we estimate magnetic field strengths in the
intergalactic medium between ~0.04 and 0.5 {\mu}G. We also comment on future
prospects of detecting more polarized sources at low frequencies.
