  Radio-loud magnetars display a wide variety of radio-pulse phenomenology
seldom seen among the population of rotation-powered pulsars.
Spectropolarimetry of the radio pulses from these objects has the potential to
place constraints on their magnetic topology and unveil clues about the
magnetar radio emission mechanism. Here we report on eight observations of the
magnetar Swift J1818.0$-$1607 taken with the Parkes Ultra-Wideband Low receiver
covering a wide frequency range from 0.7 to 4 GHz over a period of 5 months.
The magnetar exhibits significant temporal profile evolution over this period,
including the emergence of a new profile component with an inverted spectrum,
two distinct types of radio emission mode switching, detected during two
separate observations, and the appearance and disappearance of multiple
polarization modes. These various phenomena are likely a result of ongoing
reconfiguration of the plasma content and electric currents within the
magnetosphere. Geometric fits to the linearly polarized position angle indicate
we are viewing the magnetar at an angle of $\sim$99$^{\circ}$ from the spin
axis, and its magnetic and rotation axes are misaligned by $\sim$112$^{\circ}$.
While conducting these fits, we found the position angle swing had reversed
direction on MJD 59062 compared to observations taken 15 days earlier and 12
days later. We speculate this phenomena may be evidence the radio emission from
this magnetar originates from magnetic field lines associated with two
co-located magnetic poles that are connected by a coronal loop.
