Well there are different names used for the same thing, in my neck of the woods or the guys I've worked with, we always called it the stator, never the rotor, that would be confusing since the brake rotor is nearby and I don't think it's the correct term, I think the abs system uses terms also used in electric motors, but this is not an electric motor, it is a speed sensor. Anyways here is a link that describes the basic parts and they also say there are several terms for the same thing, never mentioning "rotor" as a description (which is why I chose it, LOL)
http://www2.vsm.skf.com/~/media/Files/enUS/Automotive/457102_07_09_16_22.ashx