Demagnetizer

noun

1. One who or that which removes magnetic polarity, or which causes something to cease to exert magnetic attraction; specifically, a device for removing any polarity or tendency to exert magnetic attraction from articles which have touched or have been in the sphere of action of an electromagnet, as in chucks or clutches or lifting-apparatus where the grip has been by magnetic action.
2. Any device (often a furnace) that is used to remove magnetization