  We report on a spin-orbit torque study of the spin current generation in
Cr1-xPtx alloy, using the light 3d ferromagnetic Co as the spin current
detector. We find that the dampinglike spin-orbit torque of Cr1-xPtx/Co
bilayers can be enhanced by tuning the Cr concentration in the Cr1-xPtx layer,
with a maximal value of 0.31 at the optimal composition of Cr0.2Pt0.8. We find
that the spin current generation in the Cr1-xPtx alloy can be fully understood
by the characteristic trade-off between the intrinsic spin Hall conductivity of
Pt and the carrier lifetime in the dirty limit. We find no evidence for the
spin current generation by other mechanisms in this material, revealing that
the role of Cr is found to be simply the same as other metals and oxides in
previous studies. This work also establishes the low-resistivity Cr0.2Pt0.8 as
an energy-efficient spin-orbit torque provider for magnetic memory and
computing technologies.
