  We report spin-orbit torques (SOT) in L10-ordered perpendicularly magnetized
FePt single layer, which is significantly influenced by disorder. Recently,
self-induced SOT in L10-FePt single layer has been investigated, which is
ascribed to the composition gradient along the film normal direction. However,
the determined mechanisms for magnetization switching have not been fully
studied. With varying growth temperatures, we have prepared FePt single layers
with same thickness (3 nm) but with different disordering. We have found that
nearly full magnetization switching only happens in more disordered films, and
the magnetization switching ratio becomes smaller as increasing L10 ordering.
The method for deriving effective spin torque fields in the previous studies
cannot fully explain the spin current generation and self-induced SOT in
L10-FePt single layer. Combined with Magneto-Optical Kerr Effect microscopy and
anomalous Hall effect measurements, we concluded that the disorder should
determine the formation of domain walls, as well as the spin current
generation.
