Achieving ultrahigh recording density by use of multi-stable vortex states in ferroelectric nanostructures.


Technology # 04-29 (related to technology 09-18 )


Use of Nanodots of Ferroelectric Material to Store Information (FerroElectric Memory)


This is a new invention that will revolutionize the data-storage capability of  ferroelectric random accessed memory (FRAM) by a dramatic and unprecedented increase up to a record high of 80 Terabits/inch2, which is five orders of magnitude large than those currently available. The approach is to use  our newly-discovered multiple degenerate states formed by ordered toroid moment in low-dimensional nano-scale ferroelectric structures, For instance, at low temperature, ferroelectric nanodisks of lead zirconium titanate (PZT) exhibit two robust bi-stable states with clockwise or counterclockwise concentric vortex rings, and these states with opposite toroid moments can be used as the logic states to store "O" and "1'7 in memory devices. This approach is drastically different from---and more superior than----the conventional approach where macroscopic polarization is used. In fact, macroscopic polarization does not  exist in the nanodisks and thus can not be utilized for the purpose of memory devices.

The minimum size (i.e., the diameter) of the nanodisks that display bi-stable  toroid moment in PZT is discovered to be 2.8nm, demonstrating that the ultimate storage density of our invented new app oach will be 80 Terabits/inch2. This far exceeds the current storage capability of IGbits/inch2 using magnetic recording.



The use of nanodots of ferroelectric material to store information is especially helped by the use of the vortex spin state to record the bits, because the vortex has a closed electric field that will not interact with neighboring nanodots, thus eliminating crosstalk between the memory elements. Crosstalk in conventional memory cell capacitors requires the use of passgate transistors to deal with the problem of cross talk. In addition to making memory elements for ultradense nonvolitile ferroelectric random access memory (NFERAM’s), the use of ferroelectricity in nanoscalestructures can be applied to piezoelectric sensors, efficient actuators, nanoscale dielectric capacitors for energy storage, and nanoscale ultrasounds for medical use.



Simulations by the scientists resulted in a method of changing the spin state of the vortex – allowing the possibility of writing a "1" or a "0" on each specific nanostructure such as a nanodot. The ability to change the spin state of the nanodot is based on the application of inhomogenous electric fields. Static electric charges can be placed near the nanodot and when they are switched or moved, the spin of the nanodot changes. Nanodots can then be used as memory cells, and because of the very small size of the nanodots, the density of the memory elements can go up dramatically from the 1 billion bits per square inch now achieved with magnetic recording to 80 trillion bits per square inch, or about 4 orders of magnitude greater memory density.



University of Arkansas physicists have shown that low dimensional nanoscale structures of piezoelectric materials retain their ferroelectric properties even though the piezoelectric effect disappears at the nanoscale. What happens is that the polarization of the material at the nanoscale produces a vortex where the charges swirl in a circular pattern, so that they cancel each other. The vortex of charge can then have either a clockwise or counterclockwise spin which opens up the possibility of using the spin state of the vortex to stand for either a "1" or a "0".




This invention is available for licensing. For interested parties seeking further information, feel free to contact:

Mark Allen Lanoue

Technology Manager / Tech Ventures

University of Arkansas

(479) 575-7243


Patent Information:
App Type Country Serial No. Patent No. File Date Issued Date Expire Date
Continuation in Part United States 11/811,444 7,593,250 6/8/2007 9/22/2009  
For Information, Contact:
Mark Lanoue
Technology Manager
University of Arkansas
Ivan Naumov
Laurent Bellaiche
Huaxiang Fu
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