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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Why $ \vec \mu$ is induced by $\vec B_{ext}$?

I have read that in the presence of an external magnetic field $\vec B_{ext}$ the magnetic moment induced on a paramagnetic ion is $\vec \mu=g \mu_B \vec J$ where $g$ is the Landé g-factor. Why is $\...
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Magnetic potential $\vec A$ and induction $\vec B$ [closed]

The vector potential $\vec A$ of a magnetic dipole, dipole moment $\vec m$, is given by $\vec A(\vec r) = k [ \vec m \times \vec r]$,where $k = \mu_0/4\pi r^3$. The magnetic induction $\vec B = \...
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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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Physical meaning of the form factors $F_1(q^2)$ and $F_2(q^2)$ for $q^2\neq 0$

The charge form factor $F_1(q^2)$ and the anomalous magnetic moment form factor $F_2(q^2)$ have clear interpretations at the value $q^2=0$ i.e. $F_1(0)$ is equal to the charge of the electron and $F_2(...
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How to calculate the expression for magnetic field at a position $\bf r$ based on the formula for a cylindrical magnet?

this picture is taken from "Testing a simple model for the magnetic cannon, Grigorios Magkos*, Bekari Gabritchidze and Kokkimidis Patatoukos". How should I use this to find the magnetic ...
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How to undertstand the shape of $t_{2g}$ orbital $|xy⟩\pm i|yz⟩$?

It is well defined that under the crystal field splitting, d orbital will be splitted to $e_{g}$ and $t_{2g}$ orbital. By choosing the basis as the linear combiantion of real basis, $t_{2g}$ orbital ...
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Expression for external magnetic field of a cylindrical bar magnet?

I would like to calculate the magnetic force of a cylindrical bar magnet on a steel ball bearing, which is a distance away in a straight line from one of its poles. What is the expression for this? ...
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How to obtain the torque from a magnetic moment Lagrangian?

Consider a body with magnetic dipole moment $\vec m$ subject to a magnetic field $\vec B$. We know that the torque on the body will be given by: \begin{equation} \vec \tau = \vec m \wedge \vec B \end{...
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Why don't we use earth's magnetic field to desaturate the reaction wheels of satellites?

While reading about the James Webb Telescope I learned that the sun's radiation pressure exerts a torque on Webb's big sunshield that needs to be countered by reaction wheels. Every once in a while, ...
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Conceptual explanation of Bulk Magnetization arising from atomic magnetization

I am reading about chemistry and NMR. Atoms with uneven number of protons/neutrons are magnetic, and susceptible to magnetic fields. In NMR, a sample is placed into a constant magnetic field. This ...
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Field At Point Due to Paramagnetic Material in External Field

TL;DR: How do you calculate the field at a given point when both an external field and a paramagnetic material are present? My overarching question has to do with the effect an induced magnetization (...
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Relationship between electron $g$ value and fine structure constant from QED

The wiki article on the fine structure constant says that 'The theory of QED predicts a relationship between the dimensionless magnetic moment of the electron and the fine-structure constant $\alpha$' ...
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Magnetization in Paramagnetism

I have a question regarding the magnetization of an object. Let's say this object has magnetic moments pointing in random directions, such that the total magnetization is null. If we apply an external ...
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Demagnetizing filed in magnetic moment measurements

I am interested in measuring the quantity $\vec{M}(\vec{H})$ ($\vec{M}$ is the magnetization and $\vec{H}$ is the total magnetic field within the sample) of a sample of spherical bulk material but I'm ...
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What is the definition of magnetic moment in quantum mechanics?

The general formula for the magnetic moment of a charge configuration is defined as $$\vec{\mu} = \frac{1}{2} \int \vec{r} \times \vec{J} \,d^3r$$ For an electron it's said that the correct equation ...
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Where does the 1/2 come from in integral equation for magnetic moment?

I saw that the formula for magnetic dipole moment is $$\mu=\frac{1}{2}\int\textbf{r}\times\textbf{j}\hspace{0.1cm}d^3r.$$ I understand the general intuition behind it. We are essentially summing up ...
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Torque on an anisotropic crystal in a magnetic field

while reading about crystals, I came across an equation, $\tau = M\times H $ which then writes it as $\tau_{ij} = -M_iH_j + M_jH_i$ I don't know how to drive this equation or doubt if it's even true. ...
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Why is the magnetic field around a straight current-carrying wire in concentric cirlces?

I have a question that, why are the magnetic field lines around a straight current carrying wire in the form of concentric circles? If the wire is carrying current, it is acting like a magnet. So ...
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Deuteron magnetic moment

I have a problem saying: If the magnetic moment operator of the deuteron is $$\vec{\mu}=(\mu_n+\mu_p)\vec{J}-(\mu_n +\mu_p-\frac12)\vec L$$ being $\vec J = \vec L + \vec S$ the total angular momentum ...
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Fit function for magnetization (ab plane) for $\mathrm{YBa_2Cu_3O_{6.5}}$ monocrystal, where does it come from?

So I've got this graph from a source I was told to check. It's about the measurement of magnetization in a $\mathrm{YBa_2Cu_3O_{6.5}}$ monocrystal along the $ab$ axis. The only equation in the whole ...
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Paleo-magnetism for the solar system over millions of years from the widmanstatten pattern?

I understand that the widmanstatten pattern (long fingerlike crystalline structure of iron nickel meteorites) is due to a slow cooling and solidification of asteroids over tens of millions of years. ...
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How magnets obey both law that is newton 3rd law and deflecting according to magnetic field?

I have been wondering a question that:- It is said that " magnet(say,Magnet no.1) has a magnetic field that informs in which direction the north pole (of other magnet or compass say , magnet no.2)...
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Why $\vec{\mathfrak{m}}$ and $\vec{J}$ are collinear when considering precession in magnetic field?

Recently I have read about magentization of paramagnetic materials and precession of atoms in magnetic field. So, I found the following formula: $\vec{\mathfrak{m}} = \Gamma \vec{J}$, where $\vec{\...
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Does the "demagnetizing" field inside a bar magnet try to actually demagnetize our bar magnet?

I understand mathematically why it is the case that the H must be in the opposite direction to the magnetization of the bar magnet, but I'm not quite sure what this means intuitively. This is due to $\...
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Why homogenous magnetic field is created inside a homogenously magentized sphere? And why its true for ellipsoids too?

A homogeneously magnetized sphere (magnetization vector M is constant) creates an homogeneous magnetic field inside the sphere itself. More generally, this statement remains also valid for ellipsoids ...
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Experimental data for polarization of electrons at double slits

What are the results of experiments with electrons deflected by obstacles? More in detail, what is the direction of the magnetic dipole of the electron with respect to the edge of the obstacle?
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Magnetization of vacuum fluctuation

In a simplified model one can assume that a vacuum fluctuation creates an electron-positron pair (i.e. positronium) for a short time. Let's assume a photon interacts with this vacuum fluctuation. Is ...
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Derivation of the force between two current loops [duplicate]

Could you explain me how to derive the force between two current loops carrying currents $I_1$ and $I_2$, written as a double loop integral: $$ \vec{F}_2 = \frac{\mu_0}{4 \pi} \oint \oint \frac{I_2 ...
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Electroweak contribution to the anomalous magnetic dipole moment of the muon

There are 3 diagrams that contributes to the anomalous magnetic moment of the muon (in unitary gauge): The $Z$-contribution is gauge invariant, so we can focus on diagram (i) The problem is that when ...
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