- #1
- 4,662
- 372
A derivation in Stoner's "The Demagnetizing Factors for Ellipsoids"
- Context: Graduate
- Thread starter MathematicalPhysicist
- Start date
-
- Tags
- Derivation Factors
Click For Summary
Discussion Overview
The discussion revolves around the derivation and interpretation of equations from Stoner's "The Demagnetizing Factors for Ellipsoids," specifically focusing on the relationships between magnetic fields and demagnetizing factors. Participants explore algebraic manipulations and potential inconsistencies in the equations presented in the paper.
Discussion Character
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant questions the derivation of the relation ##H-B = B/(1-D)## and seeks clarification on its origin.
- Another participant provides an algebraic manipulation of the equation ##H=-D(B-H)##, suggesting that the last equation of 1.6 requires a minus sign and notes that equation 1.7 is correct.
- A participant expresses uncertainty about whether the relation in (1.6) is derived from previous work, indicating a lack of clarity in the derivation.
- One participant asserts that there is a "typo" in equation 1.6, specifically a missing minus sign, and encourages more discussion on E&M concepts.
- A participant raises a question about a potential inconsistency in equation (4.11a) regarding the value of ##D_a##, comparing it to a later expression in the same paper.
- Another participant agrees that there seems to be an inconsistency and suggests that they would need to review earlier sections of the paper for clarification.
- One participant mentions the availability of the article on sci-hub, expressing frustration over the cost of accessing scientific papers.
- A participant reiterates their belief that the value should be 3/2, indicating a need for further review of the paper.
- There is a follow-up inquiry about whether another participant has continued reading the article, indicating ongoing engagement with the material.
Areas of Agreement / Disagreement
Participants express differing views on the correctness of the equations and the presence of typos, indicating that multiple competing interpretations exist. The discussion remains unresolved regarding the specific inconsistencies noted in the equations.
Contextual Notes
Participants highlight potential inconsistencies in the equations presented in the paper, particularly concerning the values of ##D_a## and the algebraic manipulations of the magnetic field equations. There is also mention of assumptions regarding the applied magnetic field being zero in certain equations.
- #2
- 5,996
- 3,136
##H=-D(B-H) ##. They got that part right. Let's do some algebra: ##H(1-D)=-DB ##, so that ##H=\frac{-DB}{1-D} ##. Their last equation of 1.6 needs a minus sign. ## \\ ## Note: Equation 1.6 assumes the applied magnetic field ## H_a## is zero. ## \\ ## And I also checked equation 1.7, and it is correct.
Last edited:
- #3
- 4,662
- 372
To tell you the truth I wasn't sure it's implied from the same relation in (1.6).
I thought to myself that it was some relation from previous work or somewhere else in the article.
Now that I see that's a simple matter of algebra I feel so stupid... D-:
I thought to myself that it was some relation from previous work or somewhere else in the article.
Now that I see that's a simple matter of algebra I feel so stupid... D-:
- #4
- 5,996
- 3,136
The author did have a "typo" in equation 1.6 (missing the minus sign). I'm glad you posted it. IMO more people should be studying E&M concepts such as the demagnetizing factor. We could use more E&M postings.
- #5
- 4,662
- 372
I kept on reading the paper.
On page 11 in the following attachment in eq. (4.11a) for ##D_a## after the first equality should it be ##3/4\mu^4 \ln (2m)## or as it is written there?
I am asking since after the second equality they write it as ##3/4 \mu^4 \ln (2m)##.
On page 11 in the following attachment in eq. (4.11a) for ##D_a## after the first equality should it be ##3/4\mu^4 \ln (2m)## or as it is written there?
I am asking since after the second equality they write it as ##3/4 \mu^4 \ln (2m)##.
- #6
- 5,996
- 3,136
It looks to me like it should be 3/2, but I would have to see the previous page. Clearly they have an inconsistency there.
- #7
- 4,662
- 372
It isn't discussed in the previous page.
You can find the article in sci-hub. (I know it's not really legal, but also making ordinary people who are interested in science pay lots of money for papers in science is a rip off).
You can find the article in sci-hub. (I know it's not really legal, but also making ordinary people who are interested in science pay lots of money for papers in science is a rip off).
- #8
- 4,662
- 372
Hi @Charles Link have you kept on reading this article, perhaps?Charles Link said:
I plan to return to Ashcroft and Mermin and Kittel's books once more for my Condensed Matter Physics I, hopefully now I will ace it in this summer!
- #9
- 5,996
- 3,136
No, I didn't do any additional reading of it.MathematicalPhysicist said:
Similar threads
- · Replies 4 ·
- · Replies 0 ·
- · Replies 2 ·
- · Replies 6 ·
- · Replies 50 ·
- · Replies 1 ·
- · Replies 1 ·
- · Replies 10 ·
- · Replies 4 ·
- · Replies 4 ·