And im going to stick by my guns and say the Head Motor is a Stepper in a hard disk!
The original MFM, RLL and to a lesser extent, ESDI hard drives often used stepper motors to move the heads. This was discontinued as they weren't very accurate. I worked in an industrial operation where you could see this in action. In the winter time, if you left the servers shut down overnight, the platters would shrink and the servers would not boot. You had to leave them running for 15-20 minutes to warm the drives so the platters would expand and move the tracks under the heads. Hit the reset button and the system would now boot.
All modern drive technologies use voice coil head motors. These have a very powerful permanent magnet pair with a simple coil. Varying the current through the coil moves the heads. This is used with either a servo track on one platter surface for multi platter drives or inter sector information on single platter drives to provide feedback for proper track positioning and is vastly more accurate and faster at head positioning than stepper motors could ever be.
The platter drive motor is a constant speed brushless motor.