What is a keeper for magnets?
A keeper is a steel bar or plate placed between and attached to the opposite poles of a magnet so that all the magnetism can flow from one pole to the other. The kept magnet appears completely nonmagnetic until the keeper is removed. Older alnico magnets required keepers to preserve the magnetism of these low coercivity magnets. This is useful when shipping magnets by air and for containing stray magnetism. Neodymium, samarium cobalt and ferrite magnets do not need keepers to protect their magnetism, but keepers are sometimes used to make them safer to handle.
