Talk:Electron magnetic moment

Question
I'm by no means an expert, but according to my class notes, $$\vec{\mu}_L=-\frac{e}{2m_e}\hat{\vec{L}}=-\frac{\mu_b}{\hbar}\sqrt{l(l+1)}.$$ Can someone take a look at this? Confuted —Preceding undated comment added 02:13, 23 March 2006 (UTC)
 * Just for the record protection of innocent bystanders, i mention that " confuted" would accurately describe an editor who realizes that their own idea has been proven wrong, while "Confused" might reasonably be a pseudonym chosen by a person presenting a question to an advice columnist whose work is published by a periodical. (But "Confuted" might instead be considered a riddling pseudonym of an admirer of Kung Fu-tse!) --Jerzy•t 03:43, 20 May 2018 (UTC)
 * That's the moment due to the orbital angular momentum. The electron also has an intrinsic moment, due to its spin. linas 02:42, 25 March 2006 (UTC)

Similar Question
I see written " the electron is a spin one-half particle: " quoting the magnitude of S (large S denotes electron spin) to be hbar/2. I think this should be sqrt(s*(s+1))hbar =

$$|\vec{S}| = S = \sqrt{s(s+1)}\hbar = \sqrt{\frac{1}{2} \frac{3}{2}}\hbar$$ where small $$s$$ is the spin quantum number = 1/2.

(Mark, 2011-11-21)

I have same idea. Value in the text (hbar/2) is just for z-component of spin vector. Someone mishmashed two thinks together. The last two formulas are wrong. total (spin) mag. moment = g-factor * bohr_magnetron * sqrt(3/4). z-component = g-factor * bohr_magnetron /2 =approx.= bohr_magnetron — Preceding unsigned comment added by 89.102.60.126 (talk) 17:26, 28 January 2012 (UTC)


 * This is indeed incorrect and should be changed, but I would prefer to leave the job to somebody else who knows better than me. I'd just like to note that there is a similar inaccuracy in the last sentence of Bohr magneton. Yongrenjie (talk) 10:52, 14 June 2017 (UTC)

What is written in the article is correct. We only care about the z component of the magnetic moment, since it is understood that a particle cannot simultaneously be in an eigenstate of more than one spin component. Jcline1 (talk) 01:01, 1 May 2019 (UTC)jcline1

Another question
About two thirds of the way down the page is the sentence "Where gs = 2 in Dirac mechanics, but is slightly larger due to Quantum Electrodynamic effects and where B is the magnetic field, μB is the Bohr magneton." which pertains to the equation immediately before it. B doesn't appear in this equation, whereas s (I presume spin) does. Does the fact that gs is about two and s is a half mean that prior to the advent of QED and the deviation of gs from 2 the magnetic moment of the electron was the Bohr magneton?--Chris 21:24, 29 November 2006 (UTC)

WHY DO MAGNETS EXIST AS DIPOLES? —Preceding unsigned comment added by 122.163.65.196 (talk) 10:26, 15 October 2007 (UTC)

Correction needs to be made
This article incorrectly states that the g-factor and the gyromagnetic ratio are one and the same. This is not correct. The g-factor is dimensionless, while the gyromagnetic ratio is not. 131.162.134.11 17:52, 6 April 2007 (UTC) Donald Jones (Acadia U)

g-factors The article seems to equate the g-factor to the spin g-factor. There appears to be the spin magnetic moment g-factor, the orbital magnetic moment g-factor and the total magnetic moment g-factor. The Lande g-factor seems to be for the total magnetic moment. Someone needs to clarify this. Chibibrain (talk) 20:12, 18 August 2009 (UTC)

Relation to magnetism

 * It would be nice if the article would consider more than a single electron e.g. by briefly discussing atoms/ions with more than one unpaired electron, because the article would then make more sense for people who are interested in articles like Curie constant, paramagnetism etc.

Jcwf (talk) 23:11, 2 January 2008 (UTC)

Question about electron spin energy
Dear Editor, Would you please write down the actual magnetic energy due to electron spin? In addition, please write down the predicted magnetic energy due to electron spin based on classical mechanics. And, would you please give me some references about how classical mechanics derives magnetic energy for electron spin? Thank you very much.

Sincerely, Wanchung —Preceding unsigned comment added by Wanchung Hu (talk • contribs) 09:44, 12 June 2009 (UTC)

Numerical discrepancy
The value given for the spin g-factor in this article (2.00231930419922) differs from that shown in the article on the g-factor (−2.0023193043622). Why the difference? Also, the NIST references yield a blank page. Parveson (talk) 03:04, 12 November 2011 (UTC)

new section on Pauli + dirac theories
See here, thanks. F = q(E+v×B) ⇄ ∑ici 10:19, 26 April 2012 (UTC)

Simplified explanation requested for non-experts
This page is only for physicists and explains nothing to a layman. An encyclopedia should not only be for experts. — Preceding unsigned comment added by F = |F = ]] (F = |talk]] • F = |contribs]]) 10:19, 26 April 2012

Article title?
Just as a point of consistency, I've noticed that the title of this article seems to be inconsistent with the title for neutron magnetic moment, proton magnetic moment. I don't think I know enough about the nuances to have a strong opinion as to whether anything should be changed, but it seems inconsistent. Should this article be retitled "Electron magnetic moment"? Or the other articles changed (which I'd oppose...)? Presumably the issue is just one of short hand/common usage, with "magnetic dipole moment" being formally correct, but shortened over time to just "magnetic moment". (Which likely risks possible confusion with quadrupole moments at some point.) Bdushaw (talk) 05:12, 18 January 2015 (UTC)


 * I'd support the name change to Electron magnetic moment. Anomalous magnetic dipole moment could similarly drop the "dipole" part. I'd take the argument a bit further: while the articles currently address dipole moment, the most natural place to mention nonzero higher-order (or even toroidal) magnetic moments of specific particles would be in these articles. —Quondum 00:09, 20 January 2015 (UTC)


 * I took it upon myself to make the change...apologies if I've overstretched my authority or followed the improper method... Bdushaw (talk) 01:28, 25 January 2015 (UTC)


 * Erm ... no issues of authority (we're supposed to be bold), but you appear to have used cut-and-paste to move the article content. This has the unfortunate effect of leaving the edit history behind, as well as the talk page and its edit history.  It is preferred to use the 'Move' tab at the top of the article, which automatically moves these as well (which works if the destination page is nonexistent or a "clean" redirect).  —Quondum 01:45, 25 January 2015 (UTC)


 * I undid your "renaming", but the move procedure does not work (probably because the redirect page has now developed some history). It seems we'll have to request a move (see WP:RM).  Which means we'll have to motivate it properly. —Quondum 01:58, 25 January 2015 (UTC)


 * Sorry about that...I should learn the proper procedures.  Merely motivated by the "dive in" philosophy of wikipedia.  Bdushaw (talk) 03:58, 25 January 2015 (UTC)


 * No harm done. This seems to be the standard way of learning the "proper procedures" on WP: you stumble onto them by trying.  Now we simply wait for comment, and hopefully the rename will happen in a week or so.  —Quondum 05:02, 25 January 2015 (UTC)

Requested move 25 January 2015

 * The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section. 

The result of the move request was: moved per request. Favonian (talk) 11:47, 1 February 2015 (UTC)

Electron magnetic dipole moment → Electron magnetic moment – (1) The term "electron magnetic moment" is the more common term compared to "electron magnetic dipole moment" even for when the dipole moment is meant (per both a Google search and a Google books search); (2) This article is the natural place to include magnetic moments of all orders, even though the dipole moment is the only one usually considered (one would not create separate articles for the other electron magnetic moments). —Quondum 02:22, 25 January 2015 (UTC)


 * Support per good rationale given. Dicklyon (talk) 06:54, 27 January 2015 (UTC)


 * The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Section: The classical theory of the g-factor - questions
Reading this section, I am puzzled. I sort of get what the discussion is getting at, but not really. The section suggests that the g-factor arises from a difference between mass and charge radii of the electron - a bit more background about that notion is required... Is this notion even meaningful? Is it misleading to the reader that this explanation is the origin of the g-factor? How does the equation with the ratio to the eighth power come about? Where does that come from? The result is that the mass and charge radii differ by about 9%...so what? Seems like numerology... It is all unsourced, and a brief google search turned up nothing on this sort of discussion. I'd suggest removing this section unless things can be explained better and sources for it found. Bdushaw (talk) 06:43, 19 May 2015 (UTC)


 * I think the section heading might be a little off-beam (something like "Modelling the g-factor classically" might be better). The concept is straightforward, and helps to build intuition – for example, I've often seen the (incorrect) argument that since the electron is a "point particle", mathematically it cannot rotate, its spin and its magnetic moment have no classical analogue. Models like this are important, and are an essential part of the reasoning process underlying the theory.  As presented, it is somewhat incomplete (implicitly defined variables, derivation of the g-factor from arbitrarily chosen distributions – and hence the 8th power – completely skipped), but it gives enough information to reconstruct the whole argument.  It answers the question: "Can a classical model (using special relativity and Maxwell's equations) explain a g-factor of 2?" with a clear "yes".  Intuitively, the decoupling of the mass- and charge density is classically perfectly reasonable, since most of the mass (and hence angular momentum) of the electron arises from its electromagnetic field, and the charge density arises entirely from the electron. I'd be hesitant to remove it before a more thorough reference search is made (I perceive it as having value in this context), since that order of doing things will result in the search never happening, and it is not really nonsense.  It should rather be tagged as needing references. The 9% is only useful inasmuch as it shows that we do not have to make wild assumptions about distributions of charge or mass to get this g-factor, but since the original charge and mass distributions are crude, the actual figure is irrelevant.  The implicit assumption of rigidity, and hence that the charge and mass co-rotate, is also an undue assumption once charge- and mass density are assumed decoupled, but still, the model is illustrating a valid point. —Quondum 13:51, 19 May 2015 (UTC)

Notations
There are two unspecified notations in this section of the article: N_e and N_m in
 * $$\rho_\text{e}(r) = e N_\text{e} e^{-\frac{r^2}{r_\text{e}^2}}$$

and
 * $$\rho_\text{m}(r) = m_\text{e} N_\text{m} e^{-\frac{r^2}{r_\text{m}^2}}$$

Which is signficance of these quantities? (From where do these 2 formulae derive?)--5.2.200.163 (talk) 13:14, 9 May 2016 (UTC)

Electron Spin
Electron spin can be derived directly from the pair-production energy equation,

Eν = E- + E+

Where Eν is the minimum energy of a photon when pair product occurs, E- is the mass energy of the newly created electron, and E+ is the mass energy of the newly created positron. Here, for the moment ignore any residual kinetic energy while further noting the following: for a photon, Eν = hν0, where h is Planck’s constant and ν0 is the minimum frequency of the photon that creates the particle pair, and given that h = 2πħ, where ħ is Planck’s constant divided by 2π, and that 2πν0 = ω0, where ω0 is the angular frequency equivalent of the ν0,

hν0 = E- + E+   ⇒    2πν0ħ = E- + E+   ⇒    ħω0 = E- + E+  ⇒    ħ = E-/ω0 + E+/ω0

Since the masses of electrons and positrons appear to be equal we can say that,

½ħ = E-/ω0 = E+/ω0  		eq.1

The left side of the equation is electron spin. The other side tells that for the electron (or positron) the spin is equal to the mass energy divided by the angular frequency equivalent of the photon that created the particle(s). Angular frequency implies rotational motion so the electron is energy trapped in a spherical rotation. -- 7/24/2017

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The reverted removal of „The classical theory of the g-factor“
Please don't revert edits without contentual explanation. 11:37, 20 May 2018 (UTC)

Text math renderer displays ħ as h
E.g. in the section "Spin magnetic dipole moment", the non-image math renderer displays a ħ in a fraction ($S$ = $ħ/2$) as h – on my KDE setup, in any case. Unless I'm a total exception, I would say this is suboptimal. --2A02:8071:195:2C00:0:0:0:4AF5 (talk) 22:50, 16 February 2021 (UTC)