At no additional magnetic field can be kept for a long time, the object itself magnetic. Permanent magnets with the ferromagnetic materials available, such as iron and nickel etc.
        The atomic structure, atomic itself has special strength. Usually these mineral molecules interact, magnetic area is not in the external magnetic field, but under such molecules tend to agree, just show direction of the magnetic as photonsof magnets, iron, cobalt, nickel is the most common magnetic material. Basically magnet points with magnetic permanent magnets, permanent magnets is coupled with strong magnetic magnetic material spin angular momentum into fixed and direction, Magnetic is removed, with current electric iron will slowly lose, soft magnetic. Only a magnet is appellative and tuyuhun, practical with magnetic components do not contain iron. Pure metal of iron itself is not the only permanent magnetic near permanent magnets can produce magnetic induction of general permanent magnets inside added other impurity element such as add carbon to stabilize, but such magnetic electrons will not reduce the freedom and conductive, so when the current through the bulb light does not rise, iron is common magnetic element, but many other elements has more powerful magnets, like many magnetic iron, boron is neodymium, etc.
        Resistance to permanent magnetic material is: the magnetic resistance and magnetic interference and maintain its ever magnetic measurement.