There are classes of relays that worked like that in old portable broadcast video recorders. Essentially a coil around a magnet and the coil was used to strengt

There are classes of relays that worked like that in old portable broadcast video recorders. Essentially a coil around a magnet and the coil was used to strengthen or weaken the flux with a pulse of current. The armature was spring loaded but not strong enough to release from the permanent magnet unless a pulse of "buck" current was applied. Old timey stuff.