Self Destructing Drive

Okay I recently managed to get a few hard drives, what I really have been wanting to do is make a self dustructing drive. I have done some thinking about it, and I would perfef if the ammount of damage done was limited to the drive its self, so no gun powder or thermite. I was condering somthing like a electro mag that I could put inside the drive case to wipe the bastard.

So anyone have any suggestions?

Use thermite. It will turn your drives into molten metal and shit... burns right through them.