# Questions tagged [ferromagnetism]

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### Can you have “ferromagnetic” order that preserves time-reversal symmetry?

Usually in systems with ferromagnetic order, the spin $\mathrm{O}(3) = \mathrm{SO}(3) \times Z_2^t$ (where $Z_2^t$ represents time-reversal) symmetry is broken down to $\mathrm{SO}(2)$. Is it possible ...
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### What is the formula for the gain factor of a ferromagnetic core for a torquer coil rod?

I am an undergraduate who is currently designing an actuation system for a CubeSat, more specifically a PCB magnetorquer. (with 2 ferromagnetic core coils and one air core) I made an excel sheet that ...
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### Why are there gaps between two lines of iron filings in a magnetic field?

I mean if the magnetic field is slightly increasing or decreasing at a place should'nt there be a gradient of iron filings instead of clear lines? As to me clear lines mean that there is a ...
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### Does the magnetic intensity of a iron core solenoid follow the inverse square law at distance r from the centre?

If I had an iron core solenoid, and was able to measure the force at different distances by say, using a piece of metal attached to a string on a scale, and knew current and other properties of the ...
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### Force exerted on iron particle in a magnetic field

So when an iron particle is near a permanent magnet. We see that iron particles will be attracted to the magnet and the iron particle will experience a force directed towards the north or south; is it ...
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### Precise definition of a quantum phase transition

We know that quantum phase transitions can only be accessed by varying a physical parameter. For example the strength of the external magnetic field for the Ising model. I am curious whether changing ...
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### Where are current flowing in a permanent magnet?

We know that moving charges produce magnetic fields if then all elements have electron with some non zero angular momentum so all substances must be magnetic to some extend.But this does not happen. ...
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### What is the relationship between the Ising model and a magnet's corresponding magnetic field at varying temperatures?

I understand that ferromagnetism occurs when all the spins in a magnet are aligned, leading to the magnetic vector field that we are familiar with. What happens qualitatively to the magnetic field as ...
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### Magnetic field inside a ferromagnetic material

Let us suppose there is a block of a ferromagnetic material inside a very long ideal solenoid. We know that the magnetic field lines inside are always in a straight line which will be perpendicular to ...
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### How to make sense of the side jump mechanism for anomalous Hall effect?

According to this paper, https://doi.org/10.1103/PhysRevB.2.4559, the electron (wave packet), moving along $x$ axis, undergoes a transverse shift $Δy$ after collision with spin-orbit coupling center. ...
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### Jumping ring demonstration

In demonstration of jumping ring if we assume dc source connected to solenoid, according to most of books, when we place a metallic ring over the solenoid and as soon as we turned on current, due to ...
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### Are the single-atom holmium magnets developed at IBM an example of 'spintronics'?

Phys.org IBM researchers create world's smallest magnet The above article talks about using single, individual holmium atoms in one of two states (spin-up or spin-down? Or just north-pole-up vs. down?)...
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### Energy conservation and electromagnets

I was reading here the paragraph about electromagnets. It is written that: "Electromagnets are usually in the form of iron core solenoids. The ferromagnetic property of the iron core causes the ...
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### Self-induction of a simple wire/circuit

I've been working as an EE intern for the past 5 months and have been trying to wrap my head around a couple concepts. Is the principle of self-inductance due to a circuit's inherent property of being ...
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### Numerically calculate evergy eigenvalues of spin-1/2 Heisenberg chain with nearest and next nearest neighbour interaction

I need to write a program to find the energy eigenvalues of a spin$-1/2$ Heisenberg chain with nearest and next-nearest neighbour couplings. The coupling constants should be called $J_1$ and $J_2$ ...
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### Do diamagnetics attract or repel from magnetic field strength vector direction?

If I place a ferromagnetic body in external magnetic field it will be attracted to field, and hence, body will move in the direction opposite to magnetic field strength vector direction, yes? If the ...
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### Why do ferromagnetic materials concentrate flux lines?

When a ferromagnetic material is magnetized (by application of an external magnetic field), the domains are aligned in the direction of the field, and the ferromagnetic material itself acts as magnet ...
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### Understanding magnetic hysteresis curves

Suppose I have a ferromagnetic material. It is known that the magnetization $\textbf{M}$ can be determined from a magnetic field $\textbf{H}$ using hysteresis curves as exemplified in the figure ...
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### How to understand the difference of spin wave excitation for ferromagnetism (quadratic dispersion) and anti-ferromagnetism (linear dispersion)?

As we know, the dispersion of spin excitation (magnon/spin wave) for ferromagnetic(FM) system is quadratic as $k\rightarrow 0$, but is linear for anti-ferromagnetic(AFM) system as $k\rightarrow 0$. I ...
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### Does a crystalline ferromagnetic solid break the rotational symmetry twice?

Both Heisenberg ferromagnets and crystalline solids break the rotational symmetry in space. Now consider a crystalline ferromagnetic solid. By virtue of being in a crystalline phase, it already broke ...
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### Creating a temporary magnet using a simple method

Was just wondering if someone could clarify this situation: When I take a Allen wrench and let it come in contact with an iron nail nothing happens. Not really surprising. None of the objects are ...
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### Why does the B field saturate in ferromagnetic hysteresis?

The typical hysteresis curve results from plotting $B$ and against $H$, e.g. using a Rowland ring. As I understand it, the $H$ field is that resulting from the applied current and is directly ...
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### About magnetization in ferromagnetic material

I am studying about ferromagnetism and have wondered whether the magnetization can be aligned independently of external magnetic field direction. As far as I know, the ferromagnetic material has no ...
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### Why are domains formed as separate units?

I was reading about exchange coupling and domain formation in ferromagnetic materials. As far as I can understand, some of the dipoles in the ferromagnetic material align themselves in a group called ...
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### Where does the heat due to demagnetization go?

#This is the diagram of hysterisis loop. We know due to magnetisation of a ferromagnetic metal the curve reaches (a).Later due to demagnetization the curve reaches (b) and some energy is wasted as ...
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### What contributes to the specific heat of a magnetized ferromagnetic solid?

In general, for small wavenumber, $k$, the dispersion relation of ferromagnetic spin waves is $\omega\propto k^2$ and that of phonons is $\omega\propto k$, and in 3D, the low-temperature behaviour of ...
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### Does magnetizing steel increase tensile strength?

I can't help but think that it would since even two separate pieces of magnetized steel that are just touching will have some "tensile strength". Though, I would guess that even if the answer was yes,...
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### What is short-range antiferromagnetic order?

I know what anti-ferromagnetism is. But in a paper I came across "short-range antiferromagnetic order". Can someone please explain to me what it is or suggest me the book/(or any material).
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### Why is a manget's strength measured in Teslas when magnetic field strength decreases with distance?

I am currently studying magnetism as a part of AP Physics 2, and what confused me was that a Tesla was the unit for magnetic field strength(which decreases with distance) but it was also used to ...
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### Ferromagnet Lagrangian

How to derive ferromagnet Lagrangian from the Heisenberg model: $H=-J_{ij}S_i S_j$ ? I understand how to obtain potential energy term, but it is not clear how to get "kinetic energy". \begin{equation} ...
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### Why don't ferrous metals fall to earth faster than other objects?

Given that gravity is a weak force compared with magnetism and given the fact that the earth is a magnet, why don't ferrous metals fall to earth faster than other objects? Seems like they should!
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### Force on ferromagnetic objects close to MRI magnets

I read: It is commonly stated that the force on a ferromagnetic object in the vicinity of an MRI magnet will vary as $1/x^4$. How is that?
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### Contradiction using amperes law to calculate magnetic field $B$

I am trying to study the influence on the magnetic field B generated by a solenoid in two different cases the solenoid is wound around an open iron core the solenoid is wound around a closed iron ...
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### Why do antiferromagnets occur at lower temperature than ferromagnets?

The minimal model for describing magnets is the Heisenberg Hamiltonian $$H = -\frac{1}{2}J\sum_{i,j} \mathbf{S}_i \cdot \mathbf{S}_j$$ Where $i,j$ are nearest neighbors and the factor of $1/2$ is ...
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### Ratio of $B/H$ in a ferromagnet

On the page https://en.wikipedia.org/wiki/Saturation_(magnetic), it is stated that The relation between the magnetizing field H and the magnetic field B can also be expressed as the magnetic ...
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### 1D Ising Model model montecarlo metropolis algorith simulation with external fields

Hi everyone, this is a simple simulation of the Ising model in 1D case, the algorithm is the well known metropolis one, the only difference is that I want to take into account an external magnetic ...
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### Hysteresis of a ferromagnetic material and reversibility

Suppose a virgin unmagnetized ferromagnetic sample is magnetized to complete saturation. Usually, when we reverse the magnetic field, the system does not retrace its path in the M-H plane and there is ...
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### Curie Weiss fit

I would like to know up to what point do we know our material is paramagnetic or not. I fitted a curie Weiss model in the linear region of my curves with different fields each and I am having positive ...
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### Is the boundary between ferromagnetism and paramagnetism well-defined?

I learnt that, when a ferromagnetic material is heated, it will become paramagnetic at a certain temperature. This temperature is called Curie point or Curie temperature. For example, Curie ...
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### De Almeida-Thouless line and spin glass in the Hopfield network

From the SK model, the Almeida-Thouless line appears to divide the stable paramagnetic phase and unstable spin-glass phase in the presence of an external magnetic field. However, in the case of a ...
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### Magnetic field through ferromagnetic cylinder when length is much bigger than the radius?

To preface, this is indeed a homework problem. I am a mathematician taking an electromagnetism module and have trouble wrapping my head around the problem at hand, and am struggling to start a ...
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### Induced emf inside an inductor with a ferromagnetic core

We have an AC voltage source connected to an ideal inductor that has no resistance.The inductor is wound around a ferromagnetic material.The maximum value of the driving voltage source is big enough ...