Domain wall spin torquemeter.

We report the direct measurement of the nonadiabatic component of the spin torque in domain walls. Our method is independent of both the pinning of the domain wall in the wire as well as of the Gilbert damping parameter. We demonstrate that the ratio between the nonadiabatic and the adiabatic components can be as high as 1, and explain this high value by the importance of the spin-flip rate to the nonadiabatic torque. In addition to their fundamental significance these results open the way for applications by demonstrating a significant increase of the spin torque efficiency.