A single phase electromagnetic servo-actuator that includes a rotary actuator which moves a mobile member along a limited travel including a 2N ferromagnetic pole stator structure and at least one excitation coil, the stator structure being made of a material with high magnetic permeability and a rotor having ferromagnetic yoke and a thin magnetized portion of 2N pairs of axially magnetized poles, in alternate directions, and a rotor angular position sensor, the thin magnetized portion being a separate element from the ferromagnetic yoke.