A battle of mathematical papers has broken out at arXiv.org, an online repository for academic papers, on the topic of the memristor, which may be part of the future of non-volatile memory devices.
Professor Hyongsuk Kim of the Department of Electronics Engineering at Chonbuk National University, South Korea, and two co-researchers have published a paper on arXiv.org that seeks to show that pinched hysteresis loops are the "fingerprint" of memristive devices.
Professor Kim's paper stands in direct opposition to an earlier paper on arXiv.org from Blaise Mouttet, of Arlington, Virginia, that EE Times referenced in Memristor brouhaha bubbles under.
The term memristor has been used to describe various two-terminal non-volatile memory devices currently in R&D and may have been used in patent applications, which could make apparently academic arguments about the mathematics of hysteresis curves commercially relevant.
Whereas Mouttet attempts to show that Professor Leon Chua – the circuit theorist who coined the term memristor back in 1971 – had made an error, Professor Kim and his co-authors start with criticism of Mouttet and seek to show by way of detailed mathematics that it is Mouttet who is in error and that Chua's work stands.
Professor Chua used the term memristor to describe a fourth fundamental two-terminal passive circuit element – after the resistor, capacitor and inductor. Hewlett-Packard Co. (HP) adopted the memristor term for a metal-oxide resistive RAM technology it began to develop some time before 2008.
Blaise Mouttet argues that the memory device under development at HP Labs is not a memristor but part of a broader class of variable resistance systems.
Types of non-volatile memory devices currently in the field or under development 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.
The arXiv.org system started out as a means of organizing learned paper pre-prints which had been distributed by email in the early days of internet communication. As such arXiv.org is not peer-reviewed, although it is understood that moderators do exist to categorize and re-categorize submissions.
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.
My formal response to Kim et al.'s article is available at
New Scientist has picked up the story at
There are many scientists who are actively working on memristors.
They are fascinated by the new features and enormous potential applications of the memristor. For me, I am working on memristors day and night with our students in a modestly equipped university in Korea. We who are working on memristors understood its pros and cons. Definitely, we bet on the side of success.
The memristor is a novel device whose technology is still under development. We hope to be able to contribute to its development, however small our contribution may be. Therefore, we do not appreciate Mouttet’s imprudent opinions, which are inflammatory, abusive, and have no scientific merits.
Due to Mr. Mouttet’s technically misleading and flawed assertions, I and my students have spent much of our precious times to conduct simulations using Mouttet’s examples, and we have shown that Mouttet’s assertions were contrived and technically wrong. If we do not point out Mr. Mouttet’s technical errors, many innocent researchers, including ourselves who are currently conducting research on the memristor may lose their research support from their funding agencies which may have been misled by Mouttet.
Finally, I wish to stress that Mr. Mouttet’s assertions and allegations represent only his biased opinions. In science, only true statements will stand the test of time. Any technical disagreements on memristor nomenclatures or classifications should be refereed in peer review scientific journals. Anything else will not be worth our time, nor the readers’ time.
This may be relevant. Hyongsuk Kim is a listed co-inventor (along with Leon Chua) in pending US Patent Application 2011/182104 claiming a method of implementing memristor memory. Therefore Kim may have a financial interest in discrediting anyone who questions whether all forms of resistance memory are memristors.
Calling a memristor a fundemental circuit component is a lot of hype. The symmetry is only with NONLINEAR R, L and C. To prove the memristor isn't special they also have memcapacitors and meminductors. No new property has been added to resistance, capacitance and inductance. Mem just refers to a special kind of variable component.
The more I think about it, the more I think this memristive thing won't fly for almost all resistance-based memories.
Assuming, for example, that the switching mechanism is based on some Joule heating, so there is a temperature-dependent rate, that won't be based on how much charge flows through, as the temperature becomes a steady-state value, no matter how many charges pass through.
1) The paper by Kim et al. appears to be missing the point of my paper. My point was that there are non-memristive dynamic systems that also demonstrate pinched hysteresis under some conditions. Arguing that my examples do not fall into the category of memristive systems actually supports my position rather than contradicting it. Pinched hysteresis is a property of memristors but it is also a property of other dynamic systems which are neither memristors or memristive systems. The 15 examples in my paper amply prove this.
2) The issue is more important than just patent lexicon. The issue is that the scientific method requires a correct determination that Chua's memristor model matches experimental evidence. It is entirely possible that a different model other than that proposed by Chua explains the behavior of ReRAM, phase change memory, MRAM, etc. I go into this further in a paper I posted online criticizing Stan Williams comments regarding the memristor available at
Agree Peter, I didn't think about patent application...it probably also matters at schools, the memristor needs to be taught now as the fourth electrical element (after R, L, C)...by the way is there any universally accepted abbreviation for it? M? (although M is used for mutual inductance)...Kris
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