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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1answer
2k views

Why is Ampère's law violated if there are no fringe fields?

What's wrong in this diagram? The reason is this: magnetic field lines between the two poles of magnet are perfectly straight in the given diagram, which is not possible. Fringing effect of the ...
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Can magnetic fields be redirected and focused at one point?

I know that magnetic fields can be redirected, but... given a situation where you have static magnetic field over a large area, and you want to quickly change the magnetic field strength. Is it ...
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What is the electric field generated by a spinning magnet?

Consider a cylinder of permanently magnetized material, with uniform magnetization pointing along the cylindrical symmetry axis (the $z$-direction). The magnet is rotating about its cylindrical ...
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Paradox about the Stern-Gerlach experiment with $B=0$, $\nabla B\ne 0$

In a modern interpretation of the historical Stern-Gerlach experiment, a beam of neutral silver atoms, each with spin 1/2, was sent in the z direction through a nonuniform magnetic field having both a ...
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Nuclear Magnetic Resonance (NMR) Conceptual Questions

Let $M$ be the magnetic moment of a system. Below are the Bloch equations, including the relaxation terms. $$\frac{\partial M_x}{\partial t}=({\bf M} \times \gamma {\bf H_0})_x-\frac{M_x}{T_2} $$ $$...
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Relation between magnetic moment and angular momentum — classic theory

How do I prove the relation between the vectors of magnetic moment $\vec\mu$ and angular momentum $\vec L$, $$\vec\mu=\gamma\vec L$$ ? Many text books and lecture notes about the principles of ...
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How does a spinning electron produce a magnetic field?

I learned in my undergraduate physics class that atoms have magnetic fields produced by the orbit of electrons and the spin of electrons. I understand how an orbit can induce a magnetic field because ...
7
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403 views

What is the magnetic field induced near an antiferromagnet?

A ferromagnet has a nonvanishing total magnetization which results in a finite magnetic field induced outside the magnet. For an Heisenberg antiferromagnet instead, the total magnetization is zero and ...
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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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What will happen to a permanent magnet if we keep the same magnetic poles of two magnets close together for a long time?

What will happen to permanent magnet's magnetic field or magnetic ability if we keep same magnetic poles of two permanent magnet for long time? Will any magnetic loss happen over the long period of ...
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Do magnetic field shift away from the coil that generates it?

I read about magnetic induction communication on Lockheed Martin's wireless mining communication system In this interview Warren Gross said: We generate a signal and send it through a loop that's ...
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485 views

Non-Relativistic Electron Hamiltonian

I have determined a Hamiltonian for an electron using an appropriate Lagrangian of the form $$ L=\frac{1}{2m}(m\overrightarrow{v}+\frac{q}{c}\overrightarrow{A})^2-\frac{q^2}{2mc^2}\overrightarrow{A}\...
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What is the Landé g factor?

What is the Landé g factor? I know that it gives the relation between magnetic moment and angular moment, but i wanted to know why are those magnitudes related to each other and why is the magnetic ...
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Is it possible to create only a magnetic wave?

I want to know if its possible to create only a magnetic field,which i can direct to a certain chosen object?
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369 views

Magnetic moment of uncharged particles

As we know that particles, only having charge, can have magnetic moment, then how particle like neutrino (having mass) can have magnetic moment? Don't bother about neutron because it has charge ...
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Relationship between nuclear spin and nuclear magnetic moment?

We know that nuclear magnetic moment can be expressed in terms of the expected value for nuclear spin as: $$\langle\mu\rangle =[g_lj+(g_s-g_l)\langle s_z\rangle]\frac{\mu_N}{\hbar}$$ (Cf. Krane), ...
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Intuition on Magnetic Dipoles and Magnetic Moment

1) Magnetic Moment in terms of magnetic poles: According to Wikipedia, " Magnetic poles always come in pairs, their forces partially cancel each other because while one pole pulls, the other repels. ...
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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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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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How to calculate the magnetic dipole moment of a bar magnet?

I want to calculate the force between two magnets. In a previous Phys.SE question, I was told that I needed to use the dipole-dipole interaction, but that equation depends on $m$, the magnetic dipole ...
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Force from solenoid

I'd like to approximate the force from a solenoid, or at the very least find a formula which is proportional to the force so that I can experimentally find the constant for my particular case. ...
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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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When does $\nabla \times B =0$?

In my lab, I use electromagnets to apply a magnetic gradient force to lots of very small (superparamagnetic) nanoparticles embedded in an elastic medium. I believe that these can be treated as ...
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For the transition metals, how does counting the number of up-spins and down-spins still give you a non-integer magnetic moment?

The transition metals like Fe, Co and Ni have magnetic moments of 2.2, 1.7 and 0.6 Bohr magnetons, respectively. The band theory says that you get this when you calculate the density-of-states of the ...
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Why are the magnetic moment and the angular moment related?

Why are the magnetic moment and the angular moment related? I've always read everywhere that they are related but found nowhere a satisfactory explanation of the cause
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Is neutrino really a point (fundamental) particle?

Having a non-zero magnetic moment, was a proof for neutron to not to be fundamental particle. Now we have enough literature or research work over neutrinos that have proved that neutrinos, being a ...
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Why don't alpha particles have magnetic moments?

As I understand, particles such as the neutron, whilst having no external charge still possess a magnetic moment due to the underlying charges of its components. By that logic why does the alpha ...
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Why are materials magnetic?

I have trouble understanding why some materials are magnetic. What I know so far, is that electrons are the main reason. Every single electron has a magnetic moment, which is defined as the torque it ...
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Why does Earth behave like Natural Bar Magnet?

What is the reason for the Earth to behave like a bar magnet and have poles (North and South poles)?
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What is the physical significance of the Dipole Transformation of Maxwell's Equations?

The Question Given Maxwell's equations of the form \begin{align} \bar{\nabla}\times \bar{B} = \dfrac{4\pi}{c} \bar{J} + \partial_0 \bar{E} \\ \bar{\nabla}\times \bar{E} = -\partial_0 \bar{B} \\ \bar{...
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The Einstein–de Haas effect on a ferromagnetic coil which generates the external magnetic field

The Einstein–de Haas effect, if I understand it correctly, demonstrates a deep relationship between the intrinsic angular momentum (spin) and the magnetic moment of a particle; For this reason when a ...
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Why is the neutron magnetic moment negative?

I understand that the magnetic moment is due to the quarks, but specifically why is it negative? Is it due to the two down quarks or something?
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Special relativity constrains massless electric dipoles, but not massless magnetic dipoles?

Discussion in comments on the two questions linked below leaves me confused about the following point. We expect a magnetic or electric dipole to make a field that has some universal transformation ...
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Magnetization currents (amperian currents): how to show that they are always zero in total from the definition?

For magnetic field in matter the two following amperian current densities are defined: Surface currents: u.m. $[\frac{A}{m}]$ $$J_{A,s}= \bf{M} \times \hat{n}$$ Volume currents: u.m. $[\frac{A}{m^2}...
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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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What's the difference between exchange spin wave and magnetostatic spin wave?

So far I've heard of three kinds of spin waves Magnetostatic spin waves (MSW) Dipole-exchange spin waves (DESW) Exchange spin waves (ESW) What's the difference?
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Two questions about electron's magnetic spin

Does electron's magnetic spin mean that we can think of it as having the two magnetic poles? Does the spin mean that it generates magnetic field even if it is at rest? I expect to get 'no' to both ...
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Electron to electron interaction

I am interested to know if it would be possible to calculate the magnetic attraction between two electrons at zero space between their magnetic poles against electrostatic repulsion between them in ...
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What happens when a bar magnet is cut in half?

What happens when a bar magnet is cut perpendicular to its axis of magnetization? On searching the internet, there a lot of people who suggest pole reversal occurs and the cut ends repel each other, ...
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1answer
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What is the magnetic dipole moment of a pion?

I'm writing a piece on the nuclear force. My intention was to start with the Yukawa interaction and talk about pions, using them to lead into quarks and gluons and the residual strong force and more. ...
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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
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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
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Particle deflection in a magnetic dipole field

Consider a small magnetic dipole of magnetic moment $\vec{\boldsymbol{\mu}} = (\mu_x, \; \mu_y, \; \mu_z)$ sitting at the origin. The magnetic field all around is \begin{equation}\tag{1} \mathbf{B} = ...
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Dipolar magnetic field pressure

It is relatively easy to derive the potential energy stored into the magnetic field of an uniformly magnetized sphere of radius $R$ and total magnetic moment $\mu$ : \begin{equation}\tag{1} U_{\text{...
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Why does a television image rotate to the right when one side of the magnet is applied, and to the left when the other is applied?

If you have a television that displays the image of a clockwise spiral on a white background, and you apply one side (pole) of a strong magnet such as a good size neodymium iron boron magnet - the ...
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Thought experiment with entangled electrons

Suppose we start out by having two entangled electrons. We separate them by some distance and we put one electron inside a thin loop of wire connected to an extremely sensitive voltage measuring ...
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Experimental evidence showing the kinetic energy of an electron changes in a static non-uniform magnetic field?

In a previous question, Does a magnetic field do work on an intrinsic magnetic dipole?, one highly rated answer suggested that static magnetic fields do work on intrinsic magnetic dipoles in a non-...
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How do electrons actually move in the Stern Gerlach experiment?

As I understand it, the Stern-Gerlach experiment discovered: Fire an electron horizontally through a vertical magnetic field. Then, beyond the acceleration $e \textbf{v}\times \textbf{B}$ due to its ...
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If electrons aren't revolving around the nucleus, why do atoms have orbital magnetic moment?

In most introductory textbooks, the explanation of orbital magnetic moment is based on Bohr's model and electrons orbiting around the nuclues, which can be modeled as a current loop. For example, here....
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Curie temperature and magnetization?

If an ferromagnetic object is heated and reaches Tc the magnetization gradually drops as we get closer to Tc or it's a instant drop? Can I assume as I heat the object, the magnetization is weakening ...