The more electric engine concept considers the electric motor-generators included inside aircraft reactors. Because of the environment characteristics, the problem of reducing the losses in these machines becomes crucial. For such a purpose, this paper focuses on the magnetic losses, analyzing a small (10 kW) 12-phase induction motor-generator prototype through a validated numerical approach. We demonstrate that, with respect to the more traditional Fe-Si rotor core, the use of a Fe-Co alloy in the rotor reduces the total losses of up to 1%, and specifically the iron losses up to 7%, while increasing the generated electrical power up to 3%.