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.

6
votes
0answers
1k views

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 ...
5
votes
0answers
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?
5
votes
0answers
6k views

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 ...
4
votes
0answers
157 views

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?
3
votes
0answers
129 views

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 ...
3
votes
0answers
63 views

What name would you give to the method of approximating an arbitrary magnet with many smaller dipoles?

Let's say I had an arbitrarily shaped permanent magnet, with total magnetic moment $M_{0}$. Ways to calculate the magnetic field of this magnet include an analytic solution (if one exists), as well ...
2
votes
0answers
45 views

Force caused by the magnetic field on the electron spin

I have read there are two ways to express the force caused by a variable magnetic field over a magnetic moment depending on the source of the magnetic moment since it can come from a dipole or a loop ...
2
votes
0answers
158 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 ...
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}...
2
votes
0answers
184 views

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 ...
2
votes
0answers
141 views

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 ...
2
votes
0answers
263 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: ...
2
votes
0answers
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 ...
2
votes
0answers
75 views

In quantum descriptions of atoms why are observables (which we derive from the wave function) attributed to electrons?

For example the orbital angular momentum, for the hydrogen atom. Is this the total angular momentum of the atom(electron and proton) or just the electron? I am asking because, I am learning about how ...
2
votes
0answers
98 views

What is the volume magnetization of Fe3O4 (magnetite) monodomains at room temperature?

Magnetite is great stuff for making ferrofluids and has a huge amount of literature. Yet I can't seem to find an answer to the simple question in the title. The magnetization of various bulk ...
1
vote
0answers
29 views

Query about why there is a torque on this spinning ring in a magnetic field

We learnt in class that the $\vec m\times \vec B$ is the torque of a current loop in a magnetic field. I was trying to understand this by considering the diagram above. Let the B field be pointing in ...
1
vote
0answers
10 views

Piezoelectric strain curves and magnetostrictive strain curves

I am trying to understand the differences in the strains produced in piezoelectric materials and magnetostrictive materials. Magnetostrictive materials will tend to strain the same way along the ...
1
vote
0answers
31 views

How a sphere can be assumed as dipole?

From the book introduction to electrodynamics by David Griffiths , fourth edition, page no 279, there is an example to find the magnetic field of uniformly magnetized sphere. It said the magnetic ...
1
vote
0answers
77 views

Why does magnetic dipole moment $\vec{\mu}=\gamma \vec{L} $?

I have often seen that the relationship between magnetic dipole moment $\vec \mu$ and angular momentum $\vec{L}$ expressed as $$\vec{\mu}=\gamma \vec{L} $$ But consider a current loop of a charged ...
1
vote
0answers
35 views

How much time does it take magnetization to appear, after turning on a magnetic field?

When a magnetic field ${\bf H}$ is turned on from zero, a piece of material, not previously magnetized, exhibits a magnetization ${\bf M}$ due to ${\bf H}$. According to ${\bf M} = \chi {\bf H}$, ...
1
vote
0answers
483 views

Positive and negative magnetostriction

We had the experiment demonstrating magnetostriction. We used interferometer to detect any length changes. We put the ferromagnetic material inside a coil and apply axial field. While telling about ...
1
vote
0answers
66 views

B-field and H-field opposing inside ferromagnets

I was studying Ferromagnets from several books where the authors would just state that its a notable feature of ferromagnets that, in an external B-field, the H-field opposes the B-field inside the ...
1
vote
0answers
121 views

Diamagnetic materials with negative susceptibility?

I have been learning about magnetostatics, and from reading about the existence of diamagnetic, paramagnetic and ferromagnetic materials I was under the impression that a limiting value for magnetic ...
1
vote
0answers
417 views

Surface current density (magnetic materials)

In deriving the boundary conditions for $H$ at the boundary between two media, my lecturer stated that "since there is no conduction (free) current on the Surface... the tangential components of H are ...
1
vote
0answers
43 views

Electric and magnetic dipole

How does an electric dipole and magnetic dipole physically realizable? By feeding a wire with current does that become a dipole?
1
vote
0answers
123 views

Diamagnetic Materials and their relation with temperature

What happens when a diamagnetic material is intensively cooled, considering the fact that Curies law doesn't hold good for diamagnetic materials ? What will be the effect on its magnetization ?
1
vote
0answers
36 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\...
1
vote
0answers
83 views

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 ...
1
vote
0answers
59 views

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 ...
1
vote
0answers
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. ...
1
vote
0answers
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 ...
1
vote
0answers
33 views

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 ...
1
vote
0answers
47 views

Dipoles in an external rotating field?

Consider a bunch of magnetic dipoles in $x-y$ plane in an external magnetic field $B(t)=B_0 \hat{z}+B_1(\cos\omega t~\hat{x}+\sin\omega t~\hat{y})$. The dipoles are rotating around $z$ axis and of ...
1
vote
0answers
49 views

Why is it necessary to break symmetry to get magnetoelectric effect in multiferroics?

Spatial or time symmetry needs to be broken for both magnetic and electric to happen in the same material. But how is symmetry hindering the process?
1
vote
0answers
993 views

Can (quantum) angular momentum $L$ be zero?

I am trying to calculate the orbital magnetic moment, $\bar{\mu}$, for Sodium, which has an electron configuration of $1s^2 2s^2 2p^6 3s^1$. The full shells do not contribute to $\bar{L}$ and $\bar{S}$...
1
vote
0answers
194 views

In what direction does a frustrated magnetic moment get aligned?

Consider 3 layers of Ferromagnetic materials stacked on top of each other with appropriate spacer layers in between. Let the top and bottom layers be pinned to layers of Anti Ferromagnets adjacent to ...
0
votes
0answers
23 views

Calculate the force acting on a magnet inside a solenoid wrapped in Iron

Sounds like a simple question, doesn't it? But it isn't and it has been frustrating me to no end. First, my setup is fairly straightforward: I am building an electromagnetic actuator and have a magnet ...
0
votes
0answers
37 views

Beam separation distance of silver atoms in Stern gerlach experiment

The Sge experiment is well known and the principle is well understood. I am asked the question to find the distance $d$ between the 2 beams after they are separated at the end of the magnets in the in....
0
votes
0answers
23 views

The magnetic and electric dipole moment 'popping out' from multipole expansions

I interpret electric dipole moments and magnetic dipole moments as intrinsic properties of certain materials, but in Griffiths it's literally picked out of expressing the potential and magnetic vector ...
0
votes
0answers
23 views

Hysteresis in Magnetoresistance

I am measuring the magnetoresistance of a thin ferromagnetic film from -1T to 1T, it looks something like this - The magnetoresistance increases slightly between 0 and coercivity of the film and then ...
0
votes
0answers
20 views

How to determine the best-fit magnetic dipole Gauss coefficient in a shifted coordinate system?

Introduction A planetary magnetic field $\vec{B}$ can be described outside of the planet using Gauss coefficients $g_n^m$ and $h_n^m$ and a spherical harmonic expansion: $$\vec{B} \;=\; -\vec{\...
0
votes
0answers
8 views

Is positive and negative magnetostriction attributed to the shape of the domains?

I have been reading up on magnetostriction, and noted that some materials expand while other contract in the direction of an applied magnetic field, and that it is attributed to the rotation of the ...
0
votes
0answers
19 views

Finding force from torque equation

I have read an article on electrostatics textbook that, $$\vec {F}= \nabla {\vec {\tau} }$$ Such as,the toraue equation on a magnetic dipole is $$ \vec\tau={\frac{{\mu}_0 m^2}{2\pi z^3} }\hat{z} $$ ...
0
votes
0answers
62 views

Why is the singularity not taken into account?

In this article "Reflections on Maxwell’s Treatise", Section 4.2, it says: He replaces $\mathbf{m}$ with a volume element of magnetization $\mathbf{M}\ dV$ , integrates over $V$ , and lets the same ...
0
votes
0answers
24 views

how much magnetic field is experienced at the centre of bar-magent?

What is the magnitude of magnetic field at the centre of bar magnet? What's its mathematical expression?
0
votes
0answers
23 views

Sine or cosine component of force on current carrying coil in a magnetic field

For calculating torque on a current carrying loop in a magnetic field, restoring torque that is, we use the $\tau=\vec{m} \times \vec{B}$ where $\vec{m}$ is the magnetic moment and $\vec{B}$ is the ...
0
votes
0answers
18 views

Magnetic material demagnetization through Curie temperature

It is known that some materials lose their permanent magnetic properties when they are heated above certain temperature known as Curie temperature or Curie point. As those materials are cooled down to ...
0
votes
0answers
13 views

Parameters Affecting Demagnetisation

What parameters will affect how a ferromagnetic material is demagnetised? Assuming that only changing fields will induce demagnetisation (although I suppose I could well be wrong on that one), what ...
0
votes
0answers
15 views

Relaxation spectrum and time dependence of magnetic moments

Consider a thermally isolated ferromagnetic crystal above but near its Curie temperature in a bias field such that the magnetization is essentially saturated. Now remove the bias field as fast as ...
0
votes
0answers
53 views

How is the electron $g$-factor determined?

I found a description of the experiments at CERN where a Penning trap is used to to determine the g-factor but I could not find the value of the radius of the circle of precession, nor could I (surely ...