A rotor assembly for a turbomachine having a permanent magnet electric motor that defines an axis of rotation includes a jacket member. The rotor assembly also includes a magnet member that is received within the jacket member. The magnet member has a first longitudinal end and a second longitudinal end that are separated along the axis of rotation. The rotor assembly also includes a first shaft structure that is attached to the first longitudinal end and a second shaft structure that is attached to the second longitudinal end. The magnet member is solitary and unitary and has a solid core.