At first, I will show you the principle of ferroelectric data storage in brief.
Ferroelectric materials have reversible spontanious polarization, and can be applied to data storage media.
The figure shown below schematically represents the situation that information bits are held by means of allocating upward state of spontanious polarization to "1", whereas downward state to "0".
It is known that the domain wall (or boundary of two region in which the directions of spontanious polarization are different each other) of typical ferroelectric material is as thin as the order of a few lattices. This feature is very favorable for high-density data storage.
Of course, it is useless if recorded data can not be picked up, even though high-density writing method can be realized. However, measurment of spontanious polarization direction is not so easy. (cf. "What's SNDM?")
Therefore, we propose the application of SNDM technique to the pick-up device of ferroelectric data storage. SNDM can purely electricaly detect the polarity of ferroelectrics with high resolution, and these feature can be utilized when it is used as a pick-up device.