Have you made sure it's actually magnetized and it wasn't something else such as a static charge or some glue residue holding the paperclips to the magazine?
If it really is magnetized, you have a bit of an issue.
The only do-it-yourself way I know of to demagnetize metal is to get it *really* hot (read: blowtorch). From my understanding, heating the metal past it's
Curie point will re-align enough of the molecules in a random order that the magnetic field will collapse.
Lots of places have demagnetizer machines - they're essentially alternating current electromagnets that remove the magnetic field. You could try to find someone that has one locally.
You could try to figure out which polarity your magazines have, and then stroke them for awhile with a same-polarity magnet... That might just make it worse, though. I really don't know. Anyone here remember college physics?
Another question is... Is the magnetism really hurting anything anyway?
Peace,
Pete Zaria.