Permanent magnet rotors for electric motors, particularly electric motors for use in compressors, improve the electromagnetic efficiency of the motor. The rotors can include retention of surface permanent magnets using one or more of retaining features on the motor and/or pole spacers interfacing with corresponding features on a rotor core, the use of a monolithic magnet in the rotor, and/or use of a carbon fiber sleeve. The rotor can include an eddy current shield, disposed on the rotor core, on a surface of the rotor, or located within a sleeve surrounding the rotor. The rotor can be sized such that an air-gap between the rotor and a stator of a motor using the rotor is a predetermined amount that reduces electromagnetic losses such as eddy current losses.