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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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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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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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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Inductive sensor - How does it work?

I can't understand how the system sketched here physically works: 4 = permanent magnet, with residual magnetization $B_r$ 6 = ferromagnetic core with a coil around it 7 = ferromagnetic toothed ...
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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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681 views

Contradicting forces on a circular loop under current in magnetic field?

I have the following general conceptual concern. Think of a thin conducting loop of radius $R$ placed in the $x$-$y$-plane at $z=0$. There is a homogeneous current density $\vec{j}$ running through ...
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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 ...
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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 ...
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161 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 ...
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1answer
210 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 ...
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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}...
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191 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 ...
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143 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 ...
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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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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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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 ...
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1answer
84 views

Applying downward force on someone without adding to their weight

I am creating a scenario for a superhero comic, and need help with an idea. I'd like the solution to be based in scientific theory, or at least scientific fantasy, as opposed to resorting to simply ...
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99 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 ...
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1answer
173 views

How to derive magnetic moment for integrated circuit level?

Imagine we have a circuit on the xy-plane, with a random geometry (it just need to be closed). I want to calculate the magnetic moment of this setup: $$\vec{m} = \frac{1}{2} \int_V d^3 x' \vec{x}' \...
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29 views

Force on a Magnetized Body in a Non-Uniform Magnetic Field

In Griffith's Electrodynamics, it is shown that when a magnetic moment, $\mathbf{m}$, is subjected to a non-uniform magnetic field, then it experiences a net force given by $\mathbf{F}=\mathbf{\nabla}...
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Elliptical precession of magnetic moments due to external magnetic field

I have a magnet lying in the XY plane which happens to have an in plane Anistropy along +X. If I apply a field along +Z, the magnet, if initialized not along +Z, is expected to precess about +Z. ...
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71 views

Is the magnetic dipole of the electron an intrinsic property?

The profound answer to the question How permanent magnets work? starts with Sub-atomic particles such as electrons, protons, and neutrons (and many others) have a fundamental quantity called a spin ...
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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 ...
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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 ...
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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 ...
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87 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 ...
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37 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 ${\bf M} = \chi {\bf H}$, ...
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Joining poles of bar magnet

What happens when 2 poles(i.e. noth and south) of the same bar magnet joined to each other to form circular loop?
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517 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 ...
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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 ...
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1answer
69 views

What is going on inside this disc

I recently saw a video of a copper disc repelling paper pins which I suppose are made up of steel. By watching the video carefully in slow motion, I feel there is something inside this copper disc (As ...
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128 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 ...
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433 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 ...
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45 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?
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124 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 ?
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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\...
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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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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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390 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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142 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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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 ...
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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 ...
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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?
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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 $\bar{S}$...
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195 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 ...
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Symmetry reason why magnetic dipole transitions are suppressed

In the theory of light-matter interaction, electric dipole transitions between two atomic states of same parity are forbidden. This is because the Hamiltonian conserves parity. Is there a symmetry ...
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Method for calculating nuclear magnetic moments

I am having difficulties computing the magnetic moment for an even-odd (proton-neutron) nucleus. The formula is: $$\mu_J=g_J\times j\times \mu_N$$ I checked this helpful post: When calculating ...