Disorder dependent spin–orbit torques in L10 FePt single layer

We report spin–orbit torques (SOT) in a L10-ordered perpendicularly magnetized FePt single layer, which is significantly influenced by disorder. Recently, self-induced SOT in the L10-FePt single layer has been investigated, which is ascribed to the composition gradient along the normal direction of the film. However, the determined mechanisms for magnetization switching have not been fully studied. With varying growth temperatures, we have prepared FePt single layers with the 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 with 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 the L10-FePt single layer. Combined with the 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.