Talk:Curie's law

Untitled
why is 'law' lower case? —Preceding unsigned comment added by 131.118.39.104 (talk) 20:10, 3 October 2007 (UTC)

Technical
I added the technical tag. This article stars right off on equations and gives no context to what this is at all. While this should seem obvious, wiki guidelines told me to say so on the talk page anyway. —Preceding unsigned comment added by 71.37.28.223 (talk) 14:28, 28 February 2008 (UTC)

Wrong
The derivation is wrong, probability of a state is not given like that...the person who did it fudged the positive and negative signs —Preceding unsigned comment added by 137.73.160.27 (talk) 22:15, 2 June 2010 (UTC)

Attribution of so-called 'Langevin paramagnetic equation' to Langevin
The equation referred to in the article as the 'Langevin Paramagnetic equation' was proposed by Wilhelm Lenz in his 1920 paper "Beitrag zum Verständnis der magnetischen Erscheinungen infesten Körper" (Phys. Z. 21 (1920) 613). It may be found on the second page here. The idea of the Ising Model originates from this paper.

I am not aware of Langevin, or anyone else, having preceded him, and I am further not aware of this equation having any particular name. If it is so the case that the Lenz first proposed this, then it should be originally attributed to him, and if it is the case that it is named after Langevin, explained why that is so. Is anyone else informed on this topic? — Preceding unsigned comment added by 80.189.112.54 (talk) 14:32, 2 December 2018 (UTC)

Vacuum permittivity
The vacuum permittivity constant is missing all over the article. As the initial constants are defined in SI units, I would recommend to add a μ0 in most of the equations.--ReyHahn (talk) 10:03, 10 November 2020 (UTC)

Units in lead
There is a discussion about the equation in the lead. Please see this section at WT:PHYS to join in. Primefac (talk) 16:26, 10 November 2020 (UTC)

Curie constant - Possibly glaring mistakes
Article states ...with a Curie constant given by $$C = \mu_0 n\mu^2/k_B$$ J. Coey's book is cited. I checked the book, and there seems to be a factor of 3 missing in the demoninator?

In the section "General case" it states For a two-level system with magnetic moment $$\mu$$, the formula reduces to $$C = \frac{1}{k_{\rm B}}n \mu_0 \mu^2,$$ I think the Wiki-author meant to say that for a two level system with spin 1/2, where J=S=1/2 and g=2, that $$g^2 S(S+1)=3$$. This cancels the 3 in the denominator and the formula should become $$C = \frac{1}{k_{\rm B}}n \mu_0 \mu_{\rm B}^2,$$ Importantly, it should contain $$\mu_{\rm B}^2$$, not $$\mu^2$$.

Finally, a source of possible confusion: At that moment, this $$\mu$$ is a quantum mechanical operator, and squaring it behaves differently from squaring a number (it introduces the term J(J+1)). However, operator-hats are nowhere to be found.

I have changed $$k$$ to $$k_B$$ everywhere, since previously both $$k$$ and $$k_B$$ occurred in the article and seemed to be just sloppy notation? I have also changed the statement "and g is the spin's g-factor" to "and g is the g-factor", since at this point we deal with total angular momenta J, and calling g the spin's g-factor (aka g=2) here is incorrect. 2001:9E8:89B2:9500:B505:BA89:F8CA:8C97 (talk) 13:50, 1 March 2024 (UTC)