Source : Free On-Line Dictionary of Computing

bubble memory
     
        A storage device built using materials such as gadolinium
        gallium garnet which are can be magnetised easily in only one
        direction.  A film of these materials can be created so that
        it is magnetisable in an up-down direction.  The magnetic
        fields tend to join together, some with the north pole facing
        up, some with the south.
     
        When a veritcal magnetic field is imposed on this, the areas
        in opposite alignment to the field shrink to circles, or
        'bubbles'.  A bubble can be formed by reversing the field in a
        small spot, and can be destroyed by increasing the field.
     
        Bubble memory is a kind of {non-volatile storage} but
        {EEPROM}, {Flash Erasable Programmable Read-Only Memory} and
        ferroelectric technologies, which are also non-volatile, are
        faster.
     
        ["Great Microprocessors of the Past and Present", V 4.0.0,
        John Bayko , Appendix C]
     
        (1995-02-03)