Talk:Giant magnetoresistance

Image on GMR spin valve
Just have to say that I tell students off on a weekly basis for producing images that are as poorly annotated as the one in this article. What do the arrows and lines signify? What is the circuit at the bottom of the image supposed to signify?


 * The diagram is well described in the opening lines of "Spin valve GMR". Could this be moved to the caption instead so that the diagram is understandable by itself?

The whole image is highly confusing and misleading and needs to be replaced or given a major overhaul. --Lateralis (talk) 10:27, 11 February 2008 (UTC)

I don't think so. The vertical arrows obviously denote magnetisation or spin polarisation (they are actually labelled at the top of the drawing). The nearly horizontal arrows obviously show electrical current and their kinks symbolize scattering events. What indeed needs to be clarified somehow is, that it depends on the Material used (see Nature Materials 6, 813 - 823 (2007)), which spin polarisation experiences more scattering events. -- 140.78.111.41 (talk) 14:14, 30 March 2011 (UTC)

The text states that an electron will be "scattered more if the spin of the electron is opposite to the direction of the magnetisation in the FM layer" and the image shows the scattering occurring for electrons with spin parallel to the magnetisation in the FM layer. I believe the image is incorrect and needs the wobbly lines to be redrawn. JDR89 (talk) 11:00, 12 April 2011 (UTC) JDR89


 * Correct, I never noticed that. I'll see if I can find/make a better one today.  A13ean (talk) 14:21, 12 April 2011 (UTC)

Discoverers
It is false that the team that created the first product based on GMR was led by Stuart Parkin. Stuart Parkin is well known for plagiarising other groups work. In fact the team was led by Virgil Speriosu. The idea for the spin valve originated with Bruce Gurney and Bernard Dieny, a French visiting scientist. Parkin's role in the invention of the spin valve is relatively insignificant although he made major contributions to the underlying science.

I know about this since:

a) I was already working on GMR before Dieny, Gurney and Speriosu submitted their first paper;

b) I visited IBM Almaden in 1991 and talked to the team before their work was published.

-- Alison Chaiken, alison@wsrcc.com


 * I left the "discovery" section intact, but from all the papers I have seen, GMR was actually first reported in the literature by M. N. Baibich (in an article with Albert Fert as a co-author). Is there any reason that his name has been left out of the article? Even if he was a student and Albert Fert was the driving force behind the research (always a crap excuse used by professors who want to take credit for research done by their students), the team obviously decided to put M. N. Baibich as first author on the paper and I don't see why he should be left out.


 * —Preceding unsigned comment added by Mattopia (talk • contribs) 08:53, 10 October 2005


 * I've rewritten the section, but I'm not about to start listing everybody in the research teams. Since the article is on the GMR, rather than devices based on the GMR, I have no problem in highlighting someone who made major contributions to the underlying science. Average Earthman 17:16, 10 October 2005 (UTC)

Hard drives
The article makes a few references to hard drives, and even says "As stated above, GMR has been used extensively in the read heads in modern hard drives." But isn't really "stated above" so the references are a bit confusing. Sewebster 02:37, 14 December 2006 (UTC)
 * This is fairly coherent and might provide the basis for a few sentences in the article. --JWSchmidt 14:10, 11 October 2007 (UTC)

Combine pages?
The Giant_magnetoresistive_effect and Giant_magnetoresistive pages appear to be the same, should they be combined or one of them deleted or what? —Preceding unsigned comment added by 216.162.53.230 (talk) 15:58, 12 September 2007 (UTC)


 * They appear to be the same because they are the same...one redirects to the other, which is as it should be. &mdash;Lowellian (reply) 17:26, 9 October 2007 (UTC)

Confusing Language
"The effect manifests itself as a significant decrease in resistance from the zero-field state, when the magnetization of adjacent ferromagnetic layers are antiparallel due to a weak anti-ferromagnetic coupling between layers, to a lower level of resistance when the magnetization of the adjacent layers align due to an applied external field."

This is a horrible sentence. Would someone who knows what it is trying to say please fix it. 130.225.26.145 11:23, 9 October 2007 (UTC)


 * What exactly is meant by "decrease in resistance"? What is zero-field state? Does weak anti-ferromagnetic means it is cause by the weak force?? Please! Somebody write something understandable here! (thanks).  —Preceding unsigned comment added by 83.31.67.27 (talk) 14:38, 9 October 2007 (UTC)


 * I agree that it was not coherent English. I tried to fix it based on this, but my physics knowledge is not great. --JWSchmidt 13:49, 11 October 2007 (UTC)

"Hard disk drive manufacturers are looking at such as colossal magnetoresistance effect (CMR) and giant planar Hall effect magnetic sensors." I'm guessing a word is missed out here? Does anybody know what the sentence should read? Casey boy (talk) 11:09, 15 May 2010 (UTC)

Infinitesimals
Has anyone tried to model this using infinitesimals? Tkuvho (talk) 12:46, 20 May 2011 (UTC)

Spin valve and PSEUDO Spin valve the same?

I'm preparing a presentation about GMR and was using the material from Alber Fert's Nobel lecture as a starting point and other papers that Fert was citing there. It doesn't seem that there is a "Pseudo Spin valve" since the description in that paragraph of this Wikipedia article describes exactly what happen in the spin valve. I might be wrong... Does somebody know more about this? — Preceding unsigned comment added by 35.13.182.216 (talk) 00:39, 22 November 2011 (UTC)

Pseudo-spin valve
"Pseudo-spin valve devices are very similar to the spin valve structures. The significant difference is the coercivities of the ferromagnetic layers. In a pseudo-spin valve structure a soft magnet will be used for one layer; where as a hard ferromagnet will be used for the other. This allows an applied field to flip the magnetization of the hard ferromagnet layer. For pseudo-spin valves, the non-magnetic layer thickness must be great enough so that exchange coupling minimized. This reduces the chance that the alignment of the magnetisation of adjacent layers will spontaneously change at a later time." I think this section is referring to Spin transfer torque switching in a spin valve, but I'm not sure. In any case this is not the usual use of pseudospin. Maybe something was lost in translation? A13ean (talk) 00:52, 22 November 2011 (UTC)

Part about "good conductors such as gold or copper".
Let me cite it, because it may make a lot of confusion:

"For good conductors such as gold or copper, the Fermi level lies within the hybridized sp band, and the d band is completely filled. "

I tried to search yesterday for info about how exactly bonds in copper hybridize, but I found no clue. I think, that in gold and copper the bonds are rather purely metallic - no hybridized bonds, but cloud of electrons in the whole crystal structure. The last orbital on the last shell in copper is of type "s" with one electron, and all the lower lying shells are 100% filled. What orbitals could hybridyze then? For hybridization of "s" and "p", as I understand it, we need the orbitals to be only partially filled, which is not true for "p". I think, an editor made a mistake here - maybe mixing info about hybridization of copper with oxygen in copper oxide, because oxygen has only four electrons on last "p" orbital (6 for maximal filling).

I am - however - not sure. Maybe filled valence orbitals hybridize in crystals? Appriopriate link in this section would be appreciated. — Preceding unsigned comment added by 150.254.201.241 (talk) 07:49, 14 February 2013 (UTC)
 * Thanks, you are right. The hybridization must be linked only to sp and d bands for magnetic metals in this section. I have corrected the text. --Alex-engraver (talk) 19:48, 21 May 2013 (UTC)

Definition Symbology
I just noticed that in the definition of magnetoresistence, the LaTeX uses \delta_H but the main text uses \Delta_H. I'm not sure which is more appropriate so I hesitated to make them agree, and instead chose to report it to someone who actually knows (this talk page). Either way, it could be confusing and the typography should be synchronized between formula and text. Matthew Daniels (talk) 18:04, 17 January 2014 (UTC)
 * Changed to \delta_H, which seems most appropriate among the symbols used in the literature (\Delta_H, GMR, ΔR/R). Materialscientist (talk) 01:48, 18 January 2014 (UTC)

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