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 is the "pincentrum" for magnets in the molecule structure?

So my prof explained ferromagnetism and said that permament magnets have "pincentra" so the material becomes magnetic too because the magnetic domains all point in the same direction. I don'...
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Spin Hall Effect in 2D Topological Insulator

Suppose the 2D topological insulator has the magnetic element doping in the system and the easy-axis for the magnetization is along the z axis. The the surface gap is opened due to the time-reversal ...
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Analogy between Curie's Law and the Ideal Gas Law

I've been trying to derive Curie's Law from the Ideal Gas Law for a while, since numerous sites on the internet state that they are analogous. However, if we apply the equivalences - $P \iff B$; $V \...
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What does the $B$ field refer to?

I'm just looking for some guidance, it would be nice if someone could explain this. So the $B$ field in $B=\mu H$, as I understand is the induced magnetic field in some material due to this material’s ...
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Meaning of the Eigenvalues of the Hessian Matrix in Polar Coordinates in a Ferromagnetic System

I have the Hamiltonian for a magnetostatic system (exchange, dipole-dipole, zeeman) which is in polar coordinates since the spins are confined to being in-plane. If I calculate the Hessian Matrix of ...
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When is an iron core electromagnet at its maximum strength?

If we have a solenoid electromagnet with an iron core, the magnetic field produced is proportional to the permeability of the iron and the current through the coil. As we increase the current through ...
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Thermodynamical potential to find the heat capacity at constant magnetic field $H$

Hi I am confuse with thermodynamical potentials $F$ and $G$. I am trying to find a expression for the heat capacity at constant magnetic field $H$. So I start at: $$C_h=\frac{1}{V}\left(\frac{dQ}{dT}\...
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Existence of ferroelectric domains

What is the physical logic behind the existence of ferroelectric domains? The reason for the breaking down of the ferroelectric material into domains is that "the free energy of the material ...
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Is there a non-obvious connection between nuclear stability of iron and ferromagnetism?

I find it quite remarkable that iron is the most stable nucleus, as well as the most important technical material. While its nuclear stability naturally implies that it is the most abundant material ...
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Issue with $2\pi$ in exchange-dominated dispersion relation

Suppose I have a dispersion formula given by: $\omega = \frac{2\gamma A k^2}{M_s}$, where $\gamma$ is the gyromagnetic ratio, $A$ is the exchange stiffness, $k$ is the wavevector, and $M_s$ is the ...
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Why is the remanent magnetic flux density of a ferromagnet not altered by domain boundary hindering impurities?

My understanding is that hindering the movement of domain walls within a ferromagnet (via impurities for example) would result in larger energy required to achieve saturation magnetization (and a ...
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Why is the saturation magnetisation of a ferromagnet increased by lowering temperature?

I am referring to the B-H hysteresis curve of a ferromagnet under a cycled H field I understand thermal disorder increases as higher temperatures, resulting in a transition to paramagnetism above the ...
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How to calculate the force generated from an electromagnet (or regular magnet) on a ferromagnetic material through two walls of different materials?

I am looking to estimate or quantify the force exerted upon a piece of ferromagnetic material by a magnet or electromagnet through a couple of walls made from different material each. My understanding ...
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How is polarity determined when making a permanent magnet using the "single touch" or "stroking" method?

In single touch or stroking method, a permanent magnet is "pulled" across a horizontal iron rod with one of its poles touching the rod. The diagram shows the polarity developed by the ...
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Can an incomplete steel shell contain a magnetostatic field?

I have disassembled an electric motor, and have a question about the static field of the two permanent magnets that are attached opposite each other, inside the cylindrical steel housing. They exert a ...
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Quantum vs. Classical Ising model and the Bohr van Leeuwen Theorem [duplicate]

The classical Ising model is often described as a simplistic model for ferromagnetism, and the Bohr-Van Leeuwen theorem is understood to preclude classical physics origins of magnetization in matter. ...
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Why does current reduce in step up transformer?

I have researched about it and found the laws everywhere as if lawyers have written those answer. I know the law of conservation of energy, but I don't want to think like a lawyer, I want to think ...
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Statistical physics of broken symmetry state?

If we are considering a system, like a paramagnet, above its critical temperature $T_c$ we can statistically describe it using a canonical ensemble: $$ \langle A \rangle = Tr\left[ \rho A \right]; \...
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What determines wether an interaction is ferromagnetic or antiferromagnetic?

The ferromagnetic (FM) and antiferromagnetic (AFM) interactions between atoms may be explained by exchange interactions. But what determines whether it will be FM or AFM? It seems to me that it is ...
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What is the value of the exchange field in the 3d ferromagnets ($\rm Ni, Fe, Co$)?

I have been trying to find the values of the exchange field for Ni, Co and Fe. This website mentions, "Exchange forces are very large, equivalent to a field on the order of 1000 Tesla" https:...
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Is the force applied on a ferrous object by a magnetic field determined by the field strength or its derivative?

One scenario for visualizing this question is a steel ball inside a finite solenoid. When doing that experiment myself, I notice that the ball will always roll towards the center, but the force on the ...
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Do Paramagnetic Materials become Ferromagnetic at Low Temperatures?

This is paramagentism as I understand it: Paramagnetic materials can be defined as having a low but positive magnetic susceptibility $\chi$. This low susceptibility is due to a lack of/ low ...
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Why couldn't $s$ and $p$ orbital electrons provide ferromagnetism?

I am trying to figure out why the alkali metals could NOT have Ferromagnetism, unlike iron and cobalt, alkali metals have one valence electron which provides net spin, but why could NOT the alkali ...
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Question regarding Stoner excitation in ferromagnetic metals

So upon reading through "Quantum Theory of Magnetism" by Nolting and Ramakanth I saw the derivation of the Stoner excitations as spin flip excitations (in this case for free electrons) in ...
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Why is the magnetic field produced due to a current perpendicular to the motion of current? [duplicate]

why , magnetic field produced due to current is perpendicular to the motion of current ? Why we use right hand thumb rule to get the direction of magnetic field?
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Why magnet is always a dipole?

Why magnet is alway dipole Even the atom of the magnetic substance is also dipole , how can small atom be dipole . Pls explain me
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How can different magnetic domains in a ferromagnetic material not influence any surrounding domains?

A ferromagnetic material's magnetic domains are usually drawn like this, with clearly defined domains: When not having been exposed to an external magnetic field, how can domains of a ferromagnetic ...
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Magnetic shielding VS induced magnetism

Suppose a magnet is placed on the left of an unmagnetized ferromagnetic object (imagine it as an infinite plate so no magnetic field from the magnet directly "leaks" to the other side). Does ...
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How can the exchange interaction make electron spins parallel?

Electrons repel by Coulomb interaction. When they get too close, Pauli exclusion principle ("Exchange interaction") becomes important. If their spins are parallel, they are further "...
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Why doesn't the magnetism of a magnet decrease even after continuously attracting and repeling electromagnets in a motor running for years?

I asked an electrical engineer whether he has ever opened a motor that ran for years at least 8-9 hours a day? If yes, were the magnets still powerful enough to attract/repel other magnets or irons? ...
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Ferromagnet : $N$ Spin-$1/2$ Particle on Circle

Consider one-dimensional ferromagnet namely $N$ spin-$1/2$ objects placed around a circle with the Hamiltonian $$\mathscr{H}=-\mathcal{J}\sum_{n=1}^N\vec{\mathcal{S}}_n\cdot \vec{\mathcal{S}}_{n+1}$$ ...
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importance of crystal structure for a pure iron magnet

I'm looking for a magnetic remanence comparison of alpha-iron (BCC crystal structure), gamma-iron (FCC), and amorphous-iron, all near STP (0 °C and 1 bar). Gamma-iron and amorphous-iron are not ...
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How does the metamagnetic transition occur?

How does applying a critically strong magnetic field to an antiferromagnetic material cause it to become ferromagnetic? What role does the magnetocrystalline anisotropy of the material play in this ...
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What is "magnetic instability"?

I saw "magnetic instability" many times in papers about superconductivity, but what is magnetic instability exactly? like this paper 10.1103/PhysRevB.40.10816 They only mentioned "...
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Differences between critical temperatures in Ising Model

The critical temperature $T_c$ for the 2D square lattice ferromagnetic Ising Model is known exactly to be $$T_c=\frac{2}{\ln(1+\sqrt{2})}$$. For other geometries, say, a 3D cubic lattice or a 2D ...
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Atoms in a magnetic field

If we consider electrons circulating around the nucleus in circular orbits, they constitute current loops and hence have magnetic moments (due to their orbital motion). In a paramagnetic material, for ...
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Feynman lecture 2, 36-6: How $\mu_{z}$ change with iron?

https://www.feynmanlectures.caltech.edu/II_36.html#mjx-eqn-EqII367 Feynman assumes nickel instead of iron. Without changing other assumptions, how $\mu_{z}$ change its form in case of iron? And how ...
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Are all of the aligned spins in a ferromagnet pointing in the same direction? Or does the 'south pole' consist of electrons pointing oppositely?

Are half of the electrons within a domain pointing in the opposite direction as the other half? (Separated, obviously, by a bit of a gap, otherwise they would cancel each other out...) If all of the ...
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What exactly does the frusctration mean in Kitaev spin liquids?

Sorry for asking such a basic question but I really couldn't get it. Where does the frustration come from? Some author said: "The orthogonal anisotropies of the three nearest-neighbour bonds of ...
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Magnetism in nanoparticles

Consider a ferro-, a ferri-, and a superparamagnetic material. For the same amount of magnetic material (10g each) and same magnetic field conditions, which of these three materials will develop more ...
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English translation of Preisach's paper "Über die magnetische Nachwirkung"

This paper [1] has been already cited 2000+ times according to the statistics of Google Scholar. Hence I assume there should be English translated version for such a classic paper on hysteresis but I ...
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Could you make someone magnetic without killing them? [closed]

Edit: having read some (very helpful) responses, I now think my question is closer to this: Could you, either by somehow distributing a foreign substance throughout someone's body, or by somehow ...
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Magnetic moment of carbon

I read recently the magnetic moment of carbon is zero. I am surprised how is this possible because the electronic configuration of it is $1s^2 2s^2 2p^2$. So we have two unpaired electrons here. I'll ...
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Does magnetic attraction power of magnet decay over time?

I probably have a common question to start with. Does the magnetic attraction power of a permanent magnet for example, decay over time, if the magnet is actively used to attract stuffs and perform ...
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How much Curie temperature is obtained according to the Stoner model?

In Stoner model for itinarant ferromagnetism, the spin ordering of electrons is caused by the Coulomb interaction $U$ for onsite repulsion leading to the reduction of total energy against to the ...
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Why do little chips break off so easily from strong neodymium magnets?

I have some strong toy neodymium magnets. Typically after a while little chips start breaking off, unlike from most other small metal objects, like in this image. It could of course be that neodymium ...
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Is a magnet with a magnetic remanence (Br value) of 30 feasible in any circumstances?

I am extremely unfamiliar with magnetism and electricity, but is a magnetic remanence, or Br value, of 30.25 possible? I have seen physical magnets with a Br value of around 1.2 maximum, but never ...
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Ferrocell and Quantum Decoherence

Looking upon the image shown through this device, known as the ferrocell, puts one in a position to engage in some phenomenological operation in order to know what, how and exactly why it appears in ...
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Unit to measure Ferromagnetic Strength

Imagine I have a 1T magnet that is stuck to a 3mm iron ball. Then I took some more iron balls and stuck them one under another, making a chain. Now if I do the same with cobalt or nickel, other ...
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Technical Term for Material That is Only Magnetic Next to A Magnet

I was wondering what the technical term is for some metal(like a refrigerator door) that is not magnetic on its own like neodymium but when there is a magnet in its vicinity, it attracts to the magnet....
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