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.
Questions tagged [ferromagnetism]
365 questions
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Why does the Earth even have a magnetic field?
From my knowledge of magnetism, if a magnet is heated to a certain temperature, it loses its ability to generate a magnetic field. If this is indeed the case, then why does the Earth's core, which is at a whopping 6000 °C — as hot as the sun's…
Rumplespaceking
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Would a compass with unmagnetized needle work?
We know that the needle that is used in a compass is a permanently magnetized ferromagnetic material and commonly steel is used.
If we used an unmagnetized iron needle instead, would it still align with Earth's magnetic field lines? If yes, how?
physicsguy19
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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 is more brittle than metals used for other…
doetoe
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Which mechanism causes ferromagnetism in iron?
There are at least three different mechanisms which can give rise to ferromagnetic order in iron.
First is due to the band electrons called band magnetism or itinerant magnetism which is an exchange interaction between conduction electrons.
The…
Solidification
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Microcanonical ensemble, ergodicity and symmetry breaking
In a brief introduction to statistical mechanics, that is a part of a wider course on Solid State Physics I am taking, the teacher introduced the concept of microcanonical ensemble and the ergodic hypothesis, both in its general formulation as the…
JackI
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Why don't all elements with unpaired electrons become ferromagnetic?
As a necessary condition, ferromagnetism in elements requires the existence of unpaired electrons. However, all elements with unpaired electrons are not ferromagnetic, e.g., metals such as aluminium or copper are either paramagnetic or diamagnetic.…
Solidification
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What is so special about spontaneous symmetry breaking? (time reversal example)
I have serious trouble understanding the concept of spontaneous symmetry breaking (in condensed matter specifically). Let's take time reversal in magnetic systems as an example.
Ferromagnetism is said to spontaneously breaks time reversal symmetry.…
user140255
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Magnet gyroscopic force spin
I was wondering whether a magnet exerts any measurable gyroscopic effects. I understand that magnetism is caused by alignment of spins of electrons which have angular momentum. (I realise that that they do not actually spin though), so it seems that…
user63826
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2 answers
Why do diamagnetic substances align perpendicular to the field?
My textbook says that Diamagnetic substances align their longest axis perpendicular to the field in uniform magnetic field while paramagnetic substances align their longest axis parallel to the field.
The paramagnetic case makes sense because the…
user185887
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3 answers
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 metals behave like a magnet?
I understand that…
Jack
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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 comparatively strong magnetic area next to a weaker one…
hardik kuldeep
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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 temperature for iron is given to be $1043\ \text{K}$. So as…
Vishnu
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Frustrated Ising model
Consider a 2D Ising model with nearest neighbour, and second nearest neighbour interactions
$\mathcal{H}= -J_1\sum_{\langle ij\rangle}\sigma_i \sigma_j-J_2\sum_{\langle\langle ik\rangle\rangle}\sigma_i \sigma_k$
where $\sigma =\pm 1$. And…
user183359
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Why can "Magnet-O-Meter" phone app detect magnetic objects that are not magnets?
I downloaded the "Magnet-O-Meter" Android app, that allows access to the device's magnetic field sensor. I see the measurement go up when I bring my phone near a magnet, which is to be expected, but I also see this happen when I bring the phone near…
888
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Is the susceptibility of a ferromagnet defined below the critical temperature?
The susceptibility is defined by $\chi = \partial M/ \partial H$ and for a ferromagnet above the critical temperature $T_C$, it is given by the Curie--Weiss law, $\chi \propto (T-T_C)^{-1}$.
What happens below the critical temperature? If one takes…
FusRoDah
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