# Questions tagged [magnetic-moment]

The magnetic moment of a magnet is a quantity that determines the force that the magnet can exert on electric currents and the torque that a magnetic field will exert on it. A loop of electric current, a bar magnet, an electron, a molecule, and a planet all have magnetic moments.

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### How to reduce magnetic field between two magnetic shield sheets (silicon steel sheets)?

I put 2 parallel silicon steel sheets between magnetic field as below: As silicon steel has much bigger permeability than air,magnetic line will go through 2 silicon steel sheets. What I can do to ...
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### Is it possible to introduce magnetic monopoles without breaking $∇ · B = 0$?

In another word, the net magnetic charge is always zero everywhere, which means magnetic field is still strictly source free. On the other hand, the net magnetic current jm can be nonzero, which means ...
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### What will happen when external magnetic filed disappear suddenly in Larmor precession?

Larmor precession is a phenomenon that when we place a magnetic dipole in the external magnetic field, the magnetic dipole will rotate around the direction of the magnetic field. But I am not quite ...
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### Is there an analogous potential for magnetic moments in comparison to that of electric dipoles: $\frac{k \vec{p}\cdot \hat r}{r^2}$?

If I am not mistaken the electric potential of an electric dipole is given by: $$V(r) = \frac{k | \vec{p}|\cos \theta}{r^2} = \frac{k \vec{p}\cdot \hat r}{r^2}$$ Where $\vec{p}$ is the electric ...
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### Maximum $B$-field at the surface of a permanent magnet

I have the dipole formula for a permanent spherical magnet in coordinate-free form. $\vec{B}=\frac{\mu_{0}}{4\pi}\frac{3(\vec{m}\cdot\hat{r})\hat{r}-\vec{m}}{r^{3}}$ I am trying to find the maximum $B$...
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### Why is the Anomalous magnetic dipole moment defined as half the extra contribution to the $g$-factor?

Was there a reason Julian Schwinger or Richard Feynman officially defined the anomalous magnetic moment as half of the extra $g$-factor? $$a = \frac{g-2}{2}$$ (equation is from the Wikipedia article ...
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### Magnetic moment of current loop

From what I have learnt, the magnetic moment of a current carrying loop is $$\pmb{\mu} = NI \mathbf{A}.$$ But what is written in this book Modern atomic and nuclear physics by Fuzia Yang, I am not ...
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### Quantum physics notation in statistical physics

Studying statistical physics, in particular studying paramagnets and ferromagnets, I found some quantum mechanical formulas that I don't understand how to interpret. I don't understand if they are ...
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### Deriving the magnetic field due to a dipole

I am trying to follow along with a derivation from Cullity, Introduction to magnetic materials 2011. I am getting stuck at a very early stage when computing the components of the magnetic field at a ...
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### Can fundamental particles have magnetic/electric quadrupoles, octopoles, and higher-order moments?

Fundamental particles come with magnetic and electric charge, which makes the particles into a monopole source for the magnetic and electric fields. Of course, the magnetic charge is zero for all ...
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### Is the Lorentz force law really the full (classical) characterization of how particles react to the EM field?

Classically, the effect of the electromagnetic field on particles is often said to be given by the Lorentz force law: $$\vec{F} = q\vec{E} + q\vec{v}\times\vec{B}.$$ However, I'm really starting to ...
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### What is the value of the SPIN magnetic moment of a proton?

If I understand it correctly the anomalously large total magnetic moment of the proton inside the nucleus of the atom is because it is a combinatoric particle and there are contributions by the quarks'...
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### Why is the magnetization inside a diamagnetic material antiparallel to the external field

Let's say I have a constant magnetic field and I dive into it a diamagnetic material. Griffiths says that in the presence of a magnetic field, matter becomes magnetized and it will be found to contain ...
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### Is the spin quantum number conserved during a spin flip in the Kiatev honeycomb model?

It seems that a spin flip in Kitaev honeycomb model gives an itinerant Majorana fermion and a pair of $\pi$ fluxes. Because a spin flip causes $\Delta S = 1$ and $S = 1/2$ for Majorana fermion, does ...
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### On rotating magnetic charges

Consider a sphere with magnetic charge $P$ and electric charge $Q$. We know that when the sphere is subjected to rotation about the $z$-axis, there is a magnetic dipole moment generated from the ...
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### Why do diamagnetic rods align perpendicular to the field?

My textbook says that Diamagnetic substances align their longest axis perpendicular to the field in uniform magnetic field while paramagnetic substances align their longest axis parallel to the field. ...
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### How the force on magnetic charges are introduced with magnetization field?

In the most text books used in Japanese highschools, $H$ field is introduced for magnetic field before $B$ field (flux density) is introduced. The definition in the textbooks is as follow: When a ...
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### Magnetic Flux Density in Matter

I'm working on a magnetostatic problem. I want to magnetize iron-oxide nanoparticles. I want to simulate the magnetization of said particles which depends on the magnetic flux density. Since the ...
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### How to experimentally determine the relation between magnetic moment and spin angular momentum of a quantum particle?

In quantum mechanics the spin magnetic moment in terms of angular momentum is given by $\mu=g\frac{e}{2m}L$, where $g≈2$ Now the question I was wondering, how do you determine this with experiments? I ...
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### Are permanent magnets ferromagnetic?

It is written on wiki that "Permanent magnets are made from "hard" ferromagnetic materials..." Should I conclude from it that they are ferromagnetic? For its not written that they ...
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### How to find the magnetization of a neodymium magnet?

I am interested in knowing how to find the value for Magnetisation of cylindrical N35 neodymium magnets based on the information sheet, or through the means of an experiment. this is to calculate its ...
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### Anomalous magnetic moment form factor of $e^-,\mu^-$ and $\tau^-$ in QED

The anomalous magnetic moment form factor $F(q^2)$ of an elementary fermion at $q^2=0$, calculated at one-loop, is $$F_2(0)=\frac{\alpha}{2\pi}.$$ At least at this order (order-$\alpha$), $F_2(0)$ ...
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