A permanent magnet submersible motor for electric submersible pump systems and a method of making the rotor of such a motor. The unitary construction of the rotor shaft and the yoke provides improved protection of the damage-prone magnets, while the larger effective shaft diameter also improves shaft bending resistance. Shaped form closures on the yoke promote secure magnet retention, even under highly centrifugal loads, while an exterior cladding tube and a cast resin filler material are used to further secure the magnets around the yoke periphery while also providing hermetic sealing against a working fluid.