2003 S60 rear brake rotor won't come off

I'm replacing a rear brake disc/rotor and I'm having a problem getting it off. It's either incredibly stuck, or I am missing something. I have removed the one screw on the disc that holds it to what seems to be a smaller inner disc. I have loosened the emergency/parking brake tensioner nut that is beside the parking brake lever.

The disc still won't come off. Out of desperation, I have sprayed some WD40 between the two discs. While waiting to see if that will eventually work, is there anything else that I'm missing?

Thanks