  Amorphous Tb$_{x}$Co$_{100-x}$ magnetic alloys exhibit a list of intriguing
properties, such as perpendicular magnetic anisotropy, high magneto-optical
activity and magnetization switching using ultrashort optical pulses. Varying
the Tb:Co ratio in these alloys allows for tuning properties such as the
saturation magnetic moment, coercive field and the performance of the
light-induced magnetization switching. In this work, we investigate the
magnetic, optical and magneto-optical properties of various
Tb$_{x}$Co$_{100-x}$ thin film alloy compositions. We report on the effect the
choice of different seeding layers has on the structural and magnetic
properties of Tb$_{x}$Co$_{100-x}$ layers. We also demonstrate that for a range
of alloys, deposited on fused silica substrates, with Tb content of 24-30
at.$\%$, helicity dependent all-optical switching of magnetization can be
achieved, albeit in a multi-shot framework. We explain this property to arise
from the helicity-dependent laser induced magnetization on the Co sublattice
due to the inverse Faraday effect. Our study provides an insight into material
aspects for future potential hybrid magneto-plasmonic TbCo-based architectures.
