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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Why does the magnetization of type I superconductors vanish above the critical field

The magnetization curve for type I superconductors is normally shown as the fig. bellow: where $\mu_0 H$ is the applied field, $\mu_0H_c$ the critical field and $M$ the magnetization. In general they ...
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929 views

Magnetic force from a solenoid on a ferromagnetic plunger

I'm having a hard time trying to understand a very basic electromagnetism related question, related to how a solenoid valve works. Consider the image below: Why is there a force exerted on a ...
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1answer
314 views

Wire loop oscillating inside a magnetic field (energy conservation)

Let $\vec{B}$ be an uniform magnetic field in space. I'm having problems trying to imaginate the behavior of a wire loop inside the magnetic field. First, we got that the torque $T$ will be $T$ = $\...
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3answers
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How neutrons interact if not through an electromagnetic interaction?

According to the question Do positively charged particles exchange photons? there was an answer Yes. Photons are the carriers for the electromagnetic force, regardless of the charges involved. ...
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1answer
461 views

Internal magnetic field of dipole and bar magnet

I am approximating the magnetic field of a cylindrical permanent magnet using two fictitious magnetic monopoles with separation (magnetic length) of 2L. This model is analogous to an electric dipole, ...
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1answer
314 views

Construction of constant angular velocity DC motors

In a generic DC motor model as given below, The armature is always experiencing a torque, although, varying with the angle, but how does the motor mange to achieve approximately constant angular ...
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11k views

What is the magnetic moment, and what does it have to do with the spin of the electron? [closed]

So when an object spins (like the electron), it is said to have a magnetic moment. Now, I do not understand what they mean when they say that it has a magnetic moment. When I did research, I saw this ...
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4answers
249 views

What is the shape of the detector pattern in a Stern-Gerlach experiment with a beam source (instead of a fan)?

I've been delving into Bell test experiments and woefully most sources fall into either dense physics papers, or very low level simplifications with lots of handwavium. One thing in particular I'd ...
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EMF dependence on certain variables (radius, loops and velocity)

So imagine we had a solenoid with N loops and radius r, then we dropped a magnet through the solenoid from a height of of h above the solenoid. Now when the magnet goes through the coil an emf is ...
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1answer
559 views

Classically, why is the gyromagnetic ratio always $q/2m$? [duplicate]

For uniform charge and mass distribution for a rigid body rotating with a uniform angular velocity about its centre of mass, I want to know if it is just a mathematical artifact of integration which ...
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1answer
69 views

Relationship between exp(1/z) and the magnetic field

I will preface this by saying that I'm a math student, so I know a fair bit of math but almost no physics beyond what is learned in a first year undergraduate course. I was recently looking at this ...
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Is there a mistake in these two equations describing force between magnetic dipoles?

The first equation appears here. (Force between magnets#Magnetic dipole-dipole interaction on Wikipedia) $$\mathbf{F}(\mathbf{r},\mathbf{m_1}, \mathbf{m_2}) = \frac{3\mu_0}{4\pi r^5} \left[(\mathbf{...
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Why is the spin magnetic moment for Ni$^{2+}$ given as 1.7 Bohr magnetons in some references?

I read some theoretical articles concerning Ni-O system, where Ni sits at the center of the octahedron formed by O. The calculated magnetic moment on the Ni sites are about 1.7. And these articles ...
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2answers
192 views

Atomic orbit in a magnetic field and sign conventions

Kindly refer to page 261 in the link below: Click here Griffiths claims that for an electron orbiting an origin, the centripetal acceleration is sustained by the electrical forces $\frac{1}{4 \pi \...
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Can there be precession without angular momentum?

In a wikipedia article it is said: The magnetic moment has a close connection with angular momentum called the gyromagnetic effect. This effect is expressed on a macroscopic scale in the ...
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129 views

Confusions regarding the Lorentz force

Why magnetic force isn't doing any work I know it's a similar case to centripetal force but can someone give me best possible answer not giving the dot product analogy but some high level mathematical ...
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191 views

Magnetic dipole orientation and magnetic firld gradient

Ok, if an iron atom (or anything with a magnetic dipole) sits somewhere in the region between two permanent magnets, the dipole will align itself with the resultant field in that position. However, ...
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Would setting a magnetic base to the “off” position remove the torque from an external field?

A magnetic base is a permanent magnet mostly inside a ferromagnetic case. It can be rotated so that the field is either internally shunted through the ferromagnetic blocks, or so that the blocks are ...
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1answer
125 views

Quantifying the magnetic force on a single iron atom

If a single iron atom exists in a non-uniform magnetic field, could one measure the force on it simply by multiplying the magnetic dipole moment of the atom by the change in the magnetic field?
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1answer
340 views

Motion of charged particle in uniform magnetic field

To create a uniform magnetic field I took a current carrying solenoid connected to a battery, then I took a long straight wire connected to another battery, the wire passes from inside the solenoid. ...
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1answer
138 views

Magnetic force and torque for 2D neodymium ball simulator

I'm trying to write a simulator for neoballs. I'm doing only 2D for a start, in which each ball has a magnetic moment, m, that is in the x-y plane. The simulator will use time-step integration at 60 ...
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1answer
358 views

Magnetization and magnetic moment

If a current carrying loop has magnetic moment m, how can i determine the magnetization M, of it? Ive done some reading and have found a formula that seems to solve it, it says that M is equal to the ...
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1answer
554 views

Why can't weak core-less electromagnets be used in conjunction with strong permanent magnets to perpetually harvest energy? [closed]

Why can't weak core-less electromagnets be used in conjunction with strong permanent magnets to perpetually harvest energy? Magnets will attract ferrous materials but some materials like copper or ...
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1answer
537 views

Why objects with magnetic dipole moment sometimes orient towards external B and other times they do precession?

Given the magnetic dipole moment in external uniform magnetic field $\vec{B}$, I am trying to understand why sometimes $\vec{\mu}$ simply aligns with the $\vec{B}$ and stays that way, while other ...
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489 views

Why don't the magnetic dipole moments in a neutron cancel out?

This may be a silly question. I thought magnetic dipoles were dependent on electric charge, so why in a neutron do the dipole moments not just cancel each other out?
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460 views

Moving of spin up and spin down electrons in a magnetic field [closed]

Suppose we have an electron in a conducting space, and now we apply a magnetic field. Now according to the right hand rule, the electron will have a circular motion in the plane perpendicular to the ...
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1answer
222 views

Solving a step in the derivation of the anomalous magnetic moment of the electron

In the book An Introduction to Quantum Field Theory by Peskin and Schroeder there is a derivation of the anomalous magnetic moment of the electron. The Feynman diagram to be solved is this one: and ...
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1answer
714 views

Relationship Between Magnetic Dipole Moment and Spin Angular Momentum

I am reading Introduction to Quantum Mechanics 1st edition by David J. Griffiths and I have a couple questions about this section on page 160. A spinning charged particle constitutes a magnetic ...
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1answer
105 views

Is there an easy way to see that $\phi =\frac{\mu_0}{4\pi} \frac{\vec m \cdot \vec r}{r^3}$?

The scalar potential of an electric dipole is given by: $$\phi =\frac{1}{4\pi\epsilon_0} \frac{\vec p \cdot \vec r}{r^3}$$ The derivation of this is quick, however, is there an easy way to see that ...
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380 views

Larmor precession and relaxation

I'm trying to wrap my head around Larmor precession and NMR pulses, but there's something that seems totally confusing and contradictory to me, and I haven't been able to find a definitive answer yet. ...
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1answer
403 views

Thermal equilibrium - magnetization [closed]

The electronic ground state of neutral sodium atoms in a magnetic field splits into two no longer degenerate energy states. In the thermal equilibrium the occupation probability of the states is the ...
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1answer
83 views

If $T_{kl}=\epsilon_{kil}m_i$, how to show $m_i=0.5\epsilon_{ilk}T_{lk}$? [closed]

In a book I am reading (about magnetic dipole), it is given that $T_{kl}=\epsilon_{kil}m_i$. Then, it says since $T_{kl}=-T_{lk}$, it can be shown that $m_i=0.5\epsilon_{ilk}T_{lk}$. I understand that ...
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Microscopic interpretation of magnetization in a 2D electron gas

I'm studying the de Haas-Van Alphen (dHvA) effect in a 2D free electron gas, and I have a problem to interpret the microscopical meaning of the flip of magnetization during the dHvA oscillation. My ...
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139 views

Magnetic moment of superconductors

How would a superconductor's magnetic moment be affected when it is placed in an increasing magnetic field? I know that as the magnetic field gets stronger, fluxons begin to penetrate into the ...
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134 views

Why is a particles magnetic moment proportional to its spin?

the magnetic moment of a particles is given by, m=kS, where k is a constant the gyromagnetic ratio but where does this equation come from, is it just from experiments?
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Can orbital angular momentum of an electron be changed?

In a lab at my university they are working on a project that deals with changing the "net magnetization" of a material by "flipping" the spins on some electrons. Is orbital angular momentum not ...
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Net magnetic field & magnetization on a ferromagnetic material

A ferromagnetic materiel is saturated by an exterior magnetic field like so: Where $B_1$ is a uniform magnetic field. Then after some time $t$ another magnetic field $B_2$ is introduced as well, but ...
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2answers
148 views

Current loop and direction ambiguity of the magnetic moment

Consider a circular loop in the XY-plane which carries a current $I$. Then it behaves as a magnetic dipole with moment $\textbf{m}=I\int d\textbf{S}$ where $\int d\textbf{S}$ is the area of the loop ...
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3answers
769 views

Interaction between magnetic moments and magnetic field

Consider a particle with a magnetic moment $\vec{m}$. For simplicity, suppose that this particle is a circle in the plane $xy$ which can rotate around its center of mass along the $z$ axis. If this ...
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33 views

How can an oscillating spin current in a nanostructure be observed or measured?

Through calculation it's predicted there's pure spin current oscillating in a nanostructure. Here by "pure" I mean the charge current is zero. One can imagine two electrons of opposite spin are moving ...
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264 views

When do we have a coherent magnetization rotation? (single-domain particles)

So I am studying micromagnetics + spintronics and I am little bit confused with certain concepts regarding the physics of magnetic domains (especially single domain particles): What I already knew: ...
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1answer
295 views

deflection of compass and rest position through Magnetic induction

I found a problem with a compass and a magnet, as diagrammed below. The needle of the compass was oscillating, but when a soft iron bar was placed in the "X" then the needle came to rest. Why did ...
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155 views

Adding magnetic dipoles and finding the field [closed]

If I have three magnetic dipoles and I want to model the field they produce together, how would I calculate that so I can model it in Mathematica? Assume the poles are permanent magnetic dipoles ...
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1answer
617 views

Magnetic field current loop [duplicate]

Why does a loop of irregular shape carrying current located in a magnetic field change to a circular shape? Will this always happen assuming the wire to be flexible? Even when the force is inwards? ...
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76 views

Are there experimental arguments against elementary particles to have wobbling magnetic moment

Elementary particles having angular momentum and magnetic moment are observed or assummed as these are either always parallel or antiparallel. This condition could be satisfied even the instantaneous ...
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1answer
139 views

Understanding magnetic dipole [closed]

There is a sphere of radius $R$ which is charged uniformly by charge density $\rho$. It is rotating by $\omega \hat{z}$ about $z$ axis. Find the magnetic dipole. I solve it in this way. Think of ...
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2k views

Why is the magnetic moment of a proton weaker than the electron?

I know that the nucleus of an atom does not contribute to the magnetization of an atom or material, and that the magnetic moments of protons are much weaker than electrons. Why is the magnetic moment ...
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1answer
42 views

Whats is the relationship between energy of an atom and its magnetic moment?

I'm working on a problem that says that If $\varepsilon_{\pm}=\mp (\mu \mu_0 H + k \theta \frac{M}{\mu N} )$ is the energy of the atom of a specimen that can orient itself either parallel or ...
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2answers
264 views

Domain structure and ferromagnetism and reversal of polarity

According to the domain theory, ferromagnetic substance when kept in the external strong magnetic field, it undergoes magnetisation by rotation and becomes a permanent magnet thereby even after ...
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1answer
1k views

Time-evolution of a spin-1 particle in a magnetic field

A spin-1 particle with charge $q$ and magnetic moment $\vec{\mu}=\frac{gq}{2mc}\vec{S}$ is situated in a magnetic field $B=B_0\vec{z}$. At $t=0$ the particle is found in an eigenstate $\hat{S}_y$ with ...