Amorphous TbCo thin films were deposited in a plasma-exposed region using a facing target magnetron-sputtering system with a divergent magnetic field, which can provide a large plasma potential by the loss of electrons from the plasma. The deposition parameters were controlled by changing Ar pressure and deposition distance from the center line of the system. Columnar structures were commonly observed in amorphous TbCo films, except in the films deposited at low Ar pressure. The microstructures could not be closely related with the perpendicular magnetic anisotropy of the TbCo films. The films deposited in a high plasma-exposed region showed the unusual changes in deposition rates and magnetic-compensation composition with Ar pressure, which were quantitatively analyzed.