Questions tagged [ferromagnetism]
The basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets. Ferromagnetism manifests itself in the fact that a small externally imposed magnetic field can cause the magnetic domains to align and reinforce with each other, so that the material is said to be magnetized.
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What makes iron special?
Iron is the end of the road for fission and fusion, the lowest energy nucleus. It's also the strongest magnetic atom. Is this coincidence, or is there a deeper connection?
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Measuring anistrophy of magnetic oxides
I am analyzing magnetic measurements from oxide samples, taken using a cheap sensor with the following methodology:
Aplication of elipsoidal fit.
The sensor is powered on and stabilized for 10 seconds....
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Spontaneous symmetry breaking - incorrect Peierl's argument in the continuous 3d $O(3)$ model
The following must be wrong but I don't see why:
Consider an $O(3)$ model in $d=2$ dimensions. Gapless Goldstone bosons (magnons) at $k\to 0$ are the lowest-energy excitations of the system with some ...
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Once the magnetic field lines starting from the north pole of the first magnet reach the south pole of the second magnet how do they loop back?
Gauss' law of magnetism insinuates the looped nature of magnetic field lines, the fact that they never terminate or begin like in a source-sink system. But I am having a hard time to reconcile this ...
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What equations describe magnetization of ferromagnetic materials?
When magnetic field is applied to a ferromagnetic material it magnetizes. Internal spins would be reoriented and magnetic moment would stay even after the external field is removed.
Most sources just ...
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How to obtain the Hamiltonian of the Magnon through the Hamiltonian of the electron
Suppose I already have the Hamiltonian with the atomic basis for the electron in a certain crystal structure. As usual, the atomic basis is not orthogonal, which means this Hamiltonian consists of two ...
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Magnetic Permeability and Shielding
I have two separate understandings of magnetically permeable materials and how they interact with an external magnetic field, and they don't seem to align. Can anyone point out how to connect the two ...
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Magnetic pendulum with magnetic bob
I've been reading about the common magnetic pendulum experiment in which a metal ball is swinging above more than 1 identical attracting neodymium magnets. magnetic pendulum experiment, is a ...
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Dynamics of magnetization in anisotropic ferromagnet
I am currently trying to understand how the magnetization $\mathbf{M}$ of a ferromagnet, possessing different anisotropies (shape and magnetocrystalline anisotropy), behaves in the presence of an ...
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Does the Ising model allow for quantitative predictions?
I was reading about the Ising model in a statistical mechanics book and then on Wikipedia and I understand that it is an interesting model as it allows one to make qualitative predictions about ...
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Difference between spin wave, spin density waves and charge density waves
Can someone explain where the difference between a spin wave and a spin density waves is? Also I read the term charge density waves and I am confused if it is the same as spin density waves.
Hopefully,...
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Computing and Representing Skyrmions for Different Models
Are there any example models for which Skyrmions can be explicitly constructed? Or at least a procedure where I can find analytical expressions that approximate them like a series expansion, etc. I'm ...
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Are there any "induced" forces which are repulsive in nature?
For example, London forces and induced dipole forces are both attractive forces. Additionally, when a ferromagnetic substance is placed in a magnetic field of a permanent magnet, induced magnetism ...
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Understanding the “source” of magnetic energy in a bar magnet
I’m an amateur trying to grapple around this problem of what sources the magnetic energy in a bar magnet…
We know that the source of the magnetic force that a bar magnet exerts is due to its magnetic ...
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Is spin relaxation asymmetric in magnetic semiconductors?
I am considering photo-excitation in magnetic semiconductors (e.g. metal organic frameworks). The cartoon picture is like this:
where there will be a spin polarization in the conduction band since ...
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How to calculate magnetic force produced by electromagnet through a medium at a distance
I am attempting to make a chessboard that has a strong electromagnet beneath the board, so that a piece with imbedded metal or magnet can move above the board. The image below is for reference only ...
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Mixed configuration of magneto-optical kerr effect
Typically there are three types of magneto-optical Kerr effect experiments: Polar, longitudinal, and transverse. These three geometries yield very different results regarding what is measured (...
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How to actually do calculations with the quantum-mechanical Heisenberg model?
The Heisenberg Hamiltonian in its simplest form is
$$\hat{H}= \frac{1}{2} \sum\limits_{i,j} \hat{S}_i \cdot \hat{S}_j.$$
Normally, $\hat{S}$ is assumed to be a classical vector and from this ...
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Alignment and anti-alignment of spins in magnetic field
Let's say that we spins in a very strong magnetic field. Then, the spins want to align in the same direction as the magnetic field due to torque being exerted on the spins. However, it may happen that ...
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Showing that the ground state of the Heisenberg ferromagnet is an eigenstate of the Hamiltonian
The Hamiltonian of a Heisenberg ferromagnet in terms of $S^+, S^-, S^z$ is given by:
$$H = -\frac{1}{2}|J| \sum_{i,\vec{\delta}} \left[\frac{1}{2}(S_i^+S^-_{i+\vec{\delta}} + S_i^-S^+_{i+\vec{\delta}})...
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Calculating Saturation Magnetization from Atomic Moments
I'm attempting to calculate the saturation magnetization ($M_s$) of a material based on the value of atomic magnetic moments. For instance, iron's saturation magnetization is commonly reported as 2 T (...
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Ferromagnetism vs antiferromagnetism
In ferromagnetism the spins align in the same direction, but in antiferromagnetism the spins align in the opposite direction. Both are due to the so-called 'exchange interaction', with a negative ...
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Differential magnetic susceptibility v.s. magnetic susceptibility?
For a given material which has the M-H curve looks like the following figure:
When I extract the magnetic susceptibility of the material, should I use the ratio between M and H, $\chi_m=\frac{M}{H}$, ...
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How would you calculate the FWHM of a point spread function with 2 peaks, such as those present when differentiating a hysteresis loop curve?
To evaluate the spatial resolution of an imaging system, it is common to take the FWHM of a point spread function (PSF) describing said system. In my case, the imaging system is Magnetic Particle ...
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Solving a PDE using $x-vt$ as a variable
So I was reading this Landau and Lifshitz paper:
https://doi.org/10.1016/B978-0-08-036364-6.50008-9
The article can also be found without a paywall by just searching its title, "On the Theory of ...
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Derivation in a Landau-Lifshitz ferromagnetism paper
I was reading the following paper by Landau and Lifshitz on ferromagnetism:
https://www.sciencedirect.com/science/article/abs/pii/B9780080363646500089
In the paper, the following expression is used ...
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Hysteresis curves of a ferromagnet magnetized below saturation
I am confused about the qualitative behavior of ferromagnetic materials. Referencing the diagram below, I understand that magnetizing a ferromagnet from point A to point C (its saturation ...
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Ferromagnetic substance beyond Curie's temperature
According to my textbook and various sources on internet I found that susceptibility of paramagnetic substance is related to temperature by the following formula: $$χ=Cμ_0/T$$
Susceptibility of ...
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Path of magnetization in hysteresis curve from demagnetized point
In Introduction to electrodynamics David J. Griffiths 4th edition, section 6.4.2 in magnetization of ferromagnets, after we reach the saturation point (point b in the image)
Now suppose you reduce ...
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Is there a name for a Heisenberg-like model, but instead of the ZZ operator, we have one that favor only spin-up-spin-up configurations?
I understand that the Quantum Heisenberg XXZ model in 1D has the form:
$$\hat H = \frac{1}{2} \sum_{j=1}^{N} (J_x \sigma_j^x \sigma_{j+1}^x + J_y \sigma_j^y \sigma_{j+1}^y + J_z \sigma_j^z \sigma_{j+1}...
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Time for ferromagnet to align with magnetic field
A ferromagnet is inside a solenoid. When the current in the solenoid flips its direction, the solenoid magnetic field flips. As a consequence, the ferromagnet magnetization flips.
What determines the ...
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Typically, how much could an ferromagnetic core amplify the field of a solenoid?
I have been confused by this for days. Consider a ring-shape solenoid with DC current. If we insert a ferromagetic core (cylinder) into the solenoid, how many time it could amplify the field, compared ...
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Stoner-Wohlfarth hysteresis at 0 magnetic field
There is something that is confusing me about the Stoner-Wohlfarth model. Looking at the wiki page, one sees this picture for the hysteresis loop:
The angles denoted are the angles between the field ...
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Hamiltonians with collective quantum spins and their ground states
This feels like it could be a undergrad/grad-school quantum mechanics course level problem, or potentially something pretty interesting. I'd be happy with either answer, but I don't know which one is ...
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Two-point-correlation in the 3D ising model
I am currently coding a 3D (Monte-Carlo) implementation of the Ising model, using the single spin-flip & Wolff algorithm.
So far, I was able to calculate all the interesting observables, like $M$ ...
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The mechanism of metal capturing magnetic flux
What is the mechanism of ferromagnetic object capturing magnetic flux?
For example, I learned that round metal is used in transformers to raise efficiency because the flux is carried through the metal....
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What is the difference between Curie's law and Curie-Weiss law? [closed]
Curie's Law:
$$\chi_m = \frac{C}{T}$$
Curie-Weiss law:
$$\chi_m = \frac{C}{T-T_c}$$
(C is Curie constant and $T_c$ is Curie temperature.)
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Is magnetic susceptibility infinite at Curie temperature for a ferromagnetic material?
By Curie-Weiss law , $$\chi_m = \frac{C}{T-T_c}$$ Where, C is Curie constant and $T_c$ is Curie temperature. If T = $T_c$ would then $\chi_m$ be $\infty$ ? But by theory , at Curie temperature the ...
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Why does the 'exchange interaction' in ferromagnetism favour parallel spins of electrons? Shouldn't the pauli exclusion principle hold?
I am trying to grasp the concept of the "exchange interaction" in ferromagnetism, specifically why it favors the parallel alignment of electron spins. Intuitively, one might expect the Pauli ...
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Are there thermodynamic reasons a super diamagnet cannot exist?
We define a super diamagnet as a substance which not only expels any internal magnetic fields but actually produces a stronger internal magnetic field in the opposite direction of the external field, ...
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Why Curie temperature is bigger for smaller lattice in 2D Ising model
Using Metropolis algorithm, Curie temperature was calculated for square lattices with different sizes 4x4, 8x8, 16x16 and 32x32. Here Curie temperature was estimated as temperature of maximum of heat ...
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Heisenberg ferromagnet model
I am studying some things related to the two-dimensional $xy$ model and ended up relying on the Heisenberg model to describe a ferromagnet in the presence of an external magnetic field.
\begin{...
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How can a mean-field hubbard model describe itinerant ferromagnetism?
I see some textbooks showing how Hubbard model with Mean field approximation can explain ferromagnetism of band electrons(stoner theory), but intuitively I can't understand why an on-site Hubbard ...
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Calculation of the electrical resistance of an anisotropic conductor with spacially varying current density [closed]
Fist time posting here, so I apologize in advance for the terrible editing .
I am trying to figure out a way to calculate the total resistance of a rectangular structure with known spatially dependent ...
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Ising model and the axiomatics of Statistical Mechanics
I am revisiting Statistical Mechanics to better understand models of spin glass and was wondering to what extent axiomatics of Stat.Mech. applies to an ensamble of spin configurations. In particular, ...
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Do the random-bond Ising model correlation functions decay with the disorder strength?
I'm imagining a square lattice with Ising spins on the vertices and nearest-neighbor Ising interactions. The interaction on a given bond is ferromagnetic with probability $(1-p)$ and antiferromagnetic ...
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What is the relationship between the distance of a current carrying wire and a dipole magnet's magnetic field strength?
For school, I'm doing this experiment where I measure the change in magnetic field strength, between a magnet and a current-carrying wire as a function of the distance. Online after doing some reading,...
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Attraction/repulsion forces between two magnets
If I have two identical magnets of equal strengths producing equal repulsive forces between them, and if I replace one of the magnets with a stronger magnet (everything else remaining the same), how ...
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Ground state of the Heisenberg XXX model with a coupling?
I have a one-dimensional Heisenberg chain with a Magnetic field with $N$ sites with $J>0$
\begin{equation}
\mathcal{H} = -J \sum_{i = 1}^{N-1} \vec{S_i}\cdot \vec{S_{i+1}}- \sum_{i = 1}^N \vec{H}\...
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How to interpret Magnetic Susceptibility as the ratio of two vectors $M$ and $H$, as division of two vectors is not defined in mathematics?
Magnetic Susceptibility, denoted as χ is defined as a scalar, represents the ratio between the Magnetization vector ($\vec {M}$) and the Magnetic field strength vector ($\vec{H}$).
However, in ...
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