Design of Amorphous Tb$_x$Co$_{100-x}$ Alloys for All-Optical Magnetization Switching

Amorphous TbCo 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 thesealloys 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 TbCo thin film alloy compositions. We report on the effect the choice of different seeding layers has on the structural andmagnetic properties of TbCo 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-shotframework. We explain this property to arise from the helicity-dependent laser induced magnetization on the Co sublattice dueto the inverse Faraday effect. Our study provides an insight into material aspects for future potential hybrid magneto-plasmonicTbCo-based architectures.