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.

1
vote
0answers
42 views

Is the electron a “magnetic” particle? [duplicate]

Can we consider magnetic moment an intrinsic property of the electron like its charge? Just as we say that electron is a charged particle, can we say electron is a "magnetic" particle?
3
votes
2answers
306 views

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{...
1
vote
1answer
143 views

Magnetic Torque acting on loop [closed]

I stumbled across this problem , and wondered if Torque acting on this loop can be calculated with the given information, Here is what I did : Considered that no force will be acting along the arcs....
0
votes
0answers
35 views

How do the water molecules in copper sulphate solution help to behave as a paramagnet?(compared with pure copper)

The component of magnetic moment parallel to the applied B is $\mu=-g_s\mu_Bm_S-g_L\mu_Bm_L$ if it is orbitally quenched then the $m_L$ averages to 0, and this is for non-central field. Is the ...
15
votes
3answers
784 views

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 ...
0
votes
1answer
579 views

Dipole-dipole interaction Hamiltonian

I am am just wondering how to read the well-known formula for the dipole-dipole interaction Hamiltonian. $$ \mathcal{H} = \frac{\mu^2}{2} \sum_{ij} \frac{{\bf S}_i \cdot {\bf S}_j}{r^3_{ij}} - \frac{...
0
votes
1answer
35 views

Can magnetic resonant inductive coupling work in magnetic resonance (specifically in NMR and MRI)?

Radiofrequencies are usually used to flip polarized nuclei in a magnetic field in NMR and MRI. These RF correspond to the Larmor frequency of those nuclei. Since the effect from the RF is usually due ...
3
votes
1answer
58 views

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 ...
1
vote
1answer
68 views

Do particles have magnetic poles?

Can single particles have magnetic poles? Or is it only composite structures that can have poles? If a particle can have poles, can the whole particle be classified a pole correspondingly to its ...
0
votes
1answer
577 views

What is the formula for the pull force of a cylindrical magnet

I have an axially magnetized neodymium magnet of diameter $d$ and height $h$. The material is N42. I would like to derive a formula for the pull force. This calculator does it: https://www....
0
votes
2answers
94 views

Vector field of a magnet

Given a standard reference system with axes x y z representing a 3 dimensional space and given a magnet whose north and south pole are at points $P_N=(x_N,y_N,z_N)$ and $P_S=(x_S,y_S,z_S)$ what is the ...
6
votes
1answer
461 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}\...
0
votes
0answers
47 views

In devil's staircase behaviour infinite magnetic configurations imply there's infinite magnetic energy?

Three questions about devil's staircase. First question: In devil's staircase beahviour there are infinite number of step-like structures that appear. https://www.google.es/amp/s/phys.org/news/2015-...
0
votes
1answer
69 views

Vector potential created by a magnetic moment

I want to proove that the vector potential created by a magnetic moment $\vec{m}$ is $$\vec{A}(\vec{r}) = \frac{\mu_{0}}{4\pi} \frac{\vec{m} \times \vec{u}}{r^2}$$ by using the formula $$\vec{A} = \...
1
vote
1answer
110 views

Magnetic rod in Magnetic Field [closed]

How does thin magnetic rod suspended in uniform magnetic field oscillate? I want to know what kind of oscillations will they be (displacement will be angular or linear) and which phenomenon (what ...
0
votes
1answer
128 views

What's the magnetic moment induced by an external magnetic field on a ferromagnetic material?

How do you model the magnetic moment that's induced by an external magnetic field? So basically if you have an external B field, and we put a ferromagnetic rod in that field, what would be the rod's ...
2
votes
0answers
159 views

Do antiferromagnets have hysteresis loops?

I am aware that ferromagnets have hysteresis loops and their shape depend on the relative size of magnetic interaction energy to thermal energy. I doubt if there is something equivalent to the ...
0
votes
1answer
374 views

Coordinate transform from torque along $x$, $y$, and $z$, into spherical coordinates

I am modeling a magnetic moment, $m$, and am using the sum of torques to do it. The torques are due to a time changing magnetic field, $B$, (that changes in direction and magnitude) and a dissipative ...
-2
votes
1answer
156 views

Isn't the spin only a synonym for the existence of a magnetic dipole moment and its direction?

For this question What does the magnetic moment of a quantum particle depend on? was given such statement: The magnetic moment of ... an electron, is intrinsic, and related to spin. Isn't the ...
1
vote
1answer
285 views

What does the magnetic moment of a quantum particle depend on?

Every magnetic object has a magnetic moment. From electrons to molecules, to even planets. But my question is, what determines the magnitude of a magnetic moment a quantum object has? Does the ...
1
vote
1answer
111 views

Bending a bar magnet at an angle

How can one find the expression for Magnetic moment of a magnet bent in the ratio m:n at an angle "a" (in radian). Given that the old magnetic moment (before bending) is "M" with length "l". It's ...
0
votes
1answer
1k views

Relation between angular momentum and magnetic moment of an electron (Vector Form)

Why is that minus sign be present in the ratio my text says - Mangetic moment (M)= -(e/2m)Lo where Lo is angular momentum e is the charge on an electron m is ...
1
vote
1answer
444 views

Force applied on a paramagnetic object in magnetic field

I would like to determine roughly the force applied on a paramagnetic object (for sizing calculation). But I am not use to magnetism calculation. Can someone confirm this expression of the force ...
0
votes
1answer
92 views

Demagnetization field of a prism magnet

I am studying some magnetism, and i am curious about bar magnets. Lets say you have an uniform prism magnet of Iron for example. How would you calculate the demagnetization field H which the bar ...
1
vote
1answer
376 views

Multipole expansion of the magnetic energy of a distribution of current density

My professor left me as an exercise the multipole expansion of the energy of a distribution of current density in a magnetic field but I don't manage even to understand how to start. The energy of ...
3
votes
1answer
521 views

Physical picture of spin-orbit coupling

I just want to confirm my understanding of spin-orbit coupling of a Hydrogen atom. Is the idea that the spin of the electron has a magnetic dipole moment and the orbit of the electron has a dipole ...
4
votes
2answers
169 views

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 ...
1
vote
1answer
1k views

Why electron spin being anti-parallel to the orbital angular momentum gives lower energy than the electron spin being parallel to the angular

Take hydrogen atom as example. The 2P orbital will split due to spin-orbit coupling to the $^{2}P_{3/2}$ and $^{2}P_{1/2}$ terms. The term $^{2}P_{1/2}$ has anti-parallel orientation of electron spin ...
1
vote
1answer
144 views

Current Loops VS Permanent Magnets

I'm having a hard time understanding the big connection between permanent magnets and current loops. I am aware that they both have the same magnetic field and therefore it can be said that a current ...
1
vote
1answer
826 views

What is the relation between spin waves, the Haldane gap, and a spin-1 chain?

I know that a spin wave occurs when a magnetic moment is deflected from its equilibrium position. The deflected magnetic moment will process around its equilibrium axis. Additionally, the Haldane ...
-1
votes
1answer
64 views

2 cogwheels with magnets on each cog to create infinite movement?

I have no experience of physics or what so ever but I was thinking of 2 cogwheels with magnets on each cog to create infinite movement. I have no idea on how to try this etc, but I would love to hear ...
2
votes
2answers
917 views

Calculating magnetic field

I would like to calculate the magnetic field near a neodymium magnet (N35). With near I mean I have got a rod magnet of about 10 x 4 mm and I am interested in the field from 0 mm under the magnet ...
2
votes
1answer
204 views

Magnetic moments of nucleons

I was comparing my notes of the nuclear physics class (undergraduate level) on magnetic moments of nucleons with the Krane's explanation. In my notes I wrote that there are two types of magnetic ...
0
votes
2answers
512 views

Magnetic Force of a current carrying wire loop on a magnetic object

let's say we have a current carrying wire loop WITHOUT AN EXTERNAL MAGNETIC FIELD. It produces a magnetic field on its own. what would the magnetic field and force of this loop on a charge or a ...
0
votes
0answers
40 views

Online books or articles on Ampere model

I am interested in studying Ampere model of force between magnets. Can anybody introduce me to some online books or articles on this subject. Searched the net a lot but can't find any except wikipedia....
1
vote
0answers
37 views

Dimension dependence of Curie Weiß Hamiltonian

The Hamiltonian for the Ising model on a lattice $\Lambda$ is: \begin{align} H(S) &= - J \sum\limits_{i \sim j} S_i S_j - B \sum\limits_i S_i \\ &= - J \sum\...
-2
votes
3answers
557 views

Why do we assume a neutron has no electromagnetic charge?

If a neutron has a mass ($1.674929\times 10^{-27} kg$) and all mass is defined as energy in the formula $E=mc^2$, does that mean that a neutron has an electromagnetic charge but is overall neutral, or ...
0
votes
1answer
838 views

Force/torque on a current loop due to its own magnetic field?

A current loop generates a magnetic field all around itself as shown in picture. My question is: does this magnetic field produce mechanical effects (force or torque) on the loop itself? If so, what ...
2
votes
2answers
685 views

The magnetic moment of a particle (and a neutrino)

Is the magnetic moment of a particle an intrinsic property or is there a formula to find it? What is its source? Is there a formula or a general explanation that can account for the $\mu$ of known ...
2
votes
0answers
98 views

Can an atom own a non zero total angular momentum $\bf{L}$ and a zero total magnetic moment $\bf{m}$ at the same time?

In the explanation of diamagnetism, the atoms do not have a total magnetic moment $\bf{m}$. This magnetic moment comes from the sum of all magnetic moments of electrons, that have an orbital $\bf{m_{o}...
4
votes
1answer
120 views

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}...
3
votes
1answer
457 views

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. ...
1
vote
1answer
446 views

Work on current loop placed in a magnetic field: how can there be work done against magnetic forces? [duplicate]

I'm facing some doubts while studying the lecture on magnetic dipole potential energy http://www.feynmanlectures.caltech.edu/II_15.html - "15–1 The forces on a current loop; energy of a dipole". When ...
1
vote
2answers
276 views

Spinning charged sphere, magnetic energy

I have a question about this task: Consider a thin spherical shell of dielectric which has a radius R and rotates with an angular welocity $\omega$. Suppose that the mass of the shell is negligible....
2
votes
1answer
1k views

Magnetic dipole moment of toroid

Question: Must every magnetic configuration have a north and south pole? Answer: Not necessarily. True only if the source of the field has a net non-zero magnetic moment. This is not so for a toroid ...
0
votes
1answer
432 views

Magnetic moment of the electron and gamma matrices

What is the relation between the magnetic moment of the electron and $\sigma^{\mu\nu}= \frac{i}{2}[\gamma^\mu,\gamma^\nu]$ ? that I'd like to answer this question: Consider the coupling: $\psi' \...
7
votes
1answer
397 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 ...
3
votes
1answer
3k views

Particle with spin in uniform magnetic field

In the text "Introduction to Quantum Mechanics" by Griffiths the following is stated: The magnetic dipole moment $\vec{\mu}$ is proportional to its spin angular momentum $\vec{S}$: $$\vec{\mu} = \...
0
votes
0answers
1k views

Magnetic Susceptibility of Ferromagnets

I have here a typical graph of the magnetic susceptibility against temperature for a ferromagnet. I believe I have a general understanding on why there is a general decreasing trend with temperature (...
2
votes
1answer
1k views

Magnetic Dipole Moment

I've been trying to tackle this problem for more than a day now, and would appreciate some help. The problem is to prove that the magnetic dipole moment of a spherical ball of mass $m$ and charge $Q$, ...