  The anomalous Hall effect (AHE) in L10 FePd1-xPtx alloy films is studied both
experimentally and theoretically. We find that the intrinsic contribution
(?sigma^int_AH) to the AHE can be significantly increased whereas the extrinsic
side-jump contribution (sigma^?sj_AH) can be continuously reduced from being
slightly larger than sigma^?int_AH in L10 FePd to being much smaller than
sigma^?int_AH in L10 FePt, by increasing the Pt composition x. We show that
this chemical composition tuning of the intrinsic contribution is afforded by
the stronger spin-orbit coupling strength on the Pd/Pt site when the lighter Pd
atoms are replaced by the heavier Pt atoms. Our results provide a means of
manipulating the competing AHE mechanisms in ferromagnetic alloys for fuller
understanding the AHE and also for technological applications of ferromagnetic
alloys.
