LONDON – Blaise Mouttet, of Arlington, Virginia, has published a theoretical paper on arXiv.org (see http://arxiv.org/abs/1201.2626 entitled "Memresistors and non-memristive zero-crossing hysteresis curves" that seeks to demonstrate that there are multiple dynamic systems which fall outside the constraints of the so-called memristor, two-terminal memory device and yet produce zero-crossing hysteresis curves.
The paper begins with the sentence "It has been erroneously asserted by the circuit theorist Leon Chua that all zero-crossing pinched hysteresis curves define memristors."
Blaise Mouttet argues that the interpretation of the memristor as a fourth fundamental circuit element – after the resistor, capacitor and inductor – was incorrect and that the memory device under development at HP Labs is not actually a memristor but part of a broader class of variable resistance systems.
Memristor theory was formulated and named by Professor Leon Chua in "Memristor - The missing circuit element" IEEE Trans. Circuit Theory CT-18, 507-519 (1971), which sought to define a fundamental non-linear circuit element whose existence and behavior was covered by electromagnetic theory. Hewlett-Packard Co. (HP) adopted the use of the memristor term for a metal-oxide resistive RAM technology it began to develop some time before 2008.
Mouttet presented a paper at the 2010 International Symposium on Circuits and Systems (ISCAS) that also argued that the HP Labs memory element is not a memristor and claimed that Samsung, not HP, owns the basic U.S. patent on titanium oxide resistance memory (U.S. Patent 7,417,271).
Since publishing his arXiv paper Mouttet has also been in discussion with an e-mailing list of researchers into non-volatile memory device physics.
Some e-mail correspondents have come out in favor of Mouttet's position stating that trying to define any two-terminal device in which the resistance can be altered by the current passed through the device as a memristor, adds nothing to the understanding of a complex field in which there are many types of device.
These different devices include: Resistive RAM (RRAM or ReRAM), phase-change memory (PCM) or phase-change RAM (PCRAM), conductive-bridging RAM (CBRAM), ferroelectric RAM (FRAM) as well as ferroelectric polarization memories made using organic materials.
I recently did a SPICE simulation to show that a linear resistor in parallel with a non-linear capacitor can also produce the pinched hysteresis effect (see link).
Thus pinched hysteresis cannot be considered as evidence of a "fourth fundamental circuit element" as claimed.
rbtbob-It looks interesting. I think you will find in the literature some PCM work using sub-lattice of very thin (angstroms)conductors. These were proposed, and experimental evidence presented to show application as a multi-level cell (MLC-PCM) memory device. From memory (mine)the mechanism was based on expanding the thermal core to phase change the sub-lattice chalcogenide layers. Imagine if you will a number of PCMs stacked in series in a single two terminal structure.
In the reference you cite there is a statement, room temperature and higher???
I assume the orientation of the sub lattice layers is magnetic spin not crystal orientation.
I suppose if they execute a phase change they could change the orientation. Other than materials how would be used incorporating a phase change.
Above some of the discussion has been on classification. Where would this one fit?
I would like to add from private correspondence with with Blaise Mouttet, he admonishes me:
"Incidentally, it is trivial to convert example 4 of my paper from a volatile to a non-volatile dynamic system by including a crystallization rate equation thus forming a 2nd order dynamic system. This has been discussed in phase change modeling literature by David Wright and in terms of memristive systems by DiVentra and Pershin."
He is also of the opinion:
"This is not simply a debate on semantics or classification of "memristor". In my view this entire memristor fiasco is a direct attack on the scientific method. If scientists are going around claiming they have discovered an example of a memristor (or any other theoretical concept, e.g.
Higgs boson, etc.) they need to rigorously prove that their claims have scientific validity and show comparisons between experimental data and theoretical models. This has not been done for the so-called "memristor" claims of HPLabs and it is a(expletive deleted)disgrace.
Watching this topic over the years, I've been puzzled by the firefight between two armed camps: "it's a new thing" and "it's not a new thing". I just don't understand all of the heat.
However, what does it matter? If the devices are useful, fill a niche, or enable something else, they are valuable. If they really aren't useful by reason of cost, or performance, or what-have-you, what does it matter how a memristor is classified?
Join our online Radio Show on Friday 11th July starting at 2:00pm Eastern, when EETimes editor of all things fun and interesting, Max Maxfield, and embedded systems expert, Jack Ganssle, will debate as to just what is, and is not, and embedded system.