  The discovery of all-optical ultra-fast deterministic magnetization switching
has opened up new possibilities for manipulating magnetization in devices using
femtosecond laser pulses. Previous studies on single pulse all-optical
helicity-independent switching (AO-HIS) have mainly focused on perpendicularly
magnetized thin films. This work presents a comprehensive study on AO-HIS for
in-plane magnetized GdxCo100-x thin films. Deterministic single femtosecond
laser pulse toggle magnetization switching is demonstrated in a wider
concentration range (x=10% to 25%) compared to the perpendicularly magnetized
counterparts with GdCo thicknesses up to 30 nm. The switching time strongly
depends on the GdxCo100-x concentration, with lower Gd concentration exhibiting
shorter switching times (less than 500 fs). Our findings in this geometry
provide insights into the underlying mechanisms governing single pulse AO-HIS,
which challenge existing theoretical predictions. Moreover, in-plane magnetized
GdxCo100-x thin films offer extended potential for opto-spintronic applications
compared to their perpendicular magnetized counterparts.
