LCDs are made from a fixed pixel matrix, and plasmas are of a similar design (with plasma cells instead of pixels).
Older CRTs are Cathode Ray Tubes.
This is important to understand, because the "guns" in a crt are what is affected by magnets. These guns don't exist in an LCD or a Plasma panel, so therefore, NO, they are not affected by magnets.
Note: I'm still a large beginner to this hobby, and this is only my understanding. Anyone feel free to correct me if i'm off base on this.