I think any magnetic forces will pale in comparison to chemical forces at that scale.

Why not just dip the platters in a some corrosive? I'm sure even some like drano might do the trickk.

Or perhaps how about holding the platters up to a propane torch? you wouldn't need to melt them, just get them hot enough that they lose their magnetic field.

Given that I'm at magnesium.net/~ceren, I'd hope it wouldn't require too much effort to figure out my email address.

Sheesh, some of you are so easily amused. :)