Questions tagged [ferromagnetism]

The tag has no usage guidance.

132 questions
23 views

Ferromagnetism and induced magnetism

According to Wikipedia: A magnetic domain is a region within a magnetic material where individual magnetic moments of the atoms are aligned with one another and point in the same direction thus ...
43 views

Ferromagnet $\leftrightarrow$ paramagnet at Curie temperature

I think it's like this: $\, m=\tanh\left(\frac{Bμ}{k_bT}\right)$. If now the temperature decreases, then $\mu$ increases, until it flattens out ($\tanh$ function). Is the a point where $m$ flats out, ...
12 views

ferromagnetic above the Curie temperature paramagnetic?

Why is a ferromagnet above the Curie temperature a paramagnet? Considering me, it's because a paramagnet has a higher entrope and since $\frac{1}{T} = \frac{\partial S}{\partial E}$. If T increases ...
46 views

Localization of $4f$ in rare earth and $3d$ electrons in transition metals

Is there a justification for why are the $4f$ electrons strongly localized about the nucleus in rare-earth atoms but the $3d$ electrons in transition metals extend further out from the nucleus? I have ...
14 views

Detecting if there was a repulsion or attraction on a magnet

I would like to know if we have a way of detecting if a magnet reacts to a iron bar or attract /repel by another magnet. Would be able to see through a sensor if there was some activity in the ...
39 views

Pauli matrices acting on creation operators in the second quantization formalism

I'm looking at some lecture notes for electron scattering taking place at a ferromagnet-superconductor junction. The idea is to start from a tight binding model, and eventually obtain the BdG equation....
42 views

The force involved in magnetic attraction

Magnetic field causes a force to act on moving charges as in this equation: $F = qv*B$. So what is the force that causes a magnet to attract a charge-less piece of iron? or causes the like poles of ...
159 views

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 ...
165 views

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 ...
39 views

How is the rotation of a ferromagnetic bullet affected by a coilgun?

I've been asked a question that I'm unable to answer. It's about a coilgun, and even if it could probably be expressed in simpler terms, I'll ask it in its entirety just in case I make mistakes while ...
23 views

Hysteresis in Magnetoresistance

I am measuring the magnetoresistance of a thin ferromagnetic film from -1T to 1T, it looks something like this - The magnetoresistance increases slightly between 0 and coercivity of the film and then ...
61 views

Why an insufficient overlap cause vanishing exchange interaction?

Why should the exchange interaction vanish if the atoms do not have sufficient overlap in their overfunctions? For exchange interaction not to vanish, the only requirement seems to be that the ...
82 views

Ferromagnetism - computational physics

The autocorrelation of the magnetisation is plotted for the Ising model of a ferromagnet. The critical temperature is 2.3 J/k Is this the expected behaviour? as in, it decays super fast for ...
40 views

Coercivity of pure iron

Coercivity of 99.8% pure iron is 1 oe but that of 99.95% pure iron is 0.05 oe.Why such difference while both have same retentivity? Edit: I mean to say if both have same amount of residual magnetism ...
64 views

Do magnets lose some form of energy while attracting each other? [duplicate]

Consider two very strong magnets, one above a wooden table, one below a wooden table. As the two magenets clamp together, wedging the tableplate between them, at least the bottom magnet will ...
70 views

What is the explanation behind this weird hysteresis graph?

We were doing an experiment with Ferrite material to find the Curie temperature of the material. We found that at some temperature range, there are two loops at the two ends of the curve. What is the ...
70 views

Why do spinning electrons generate magnetic dipole moments?

Can the spin of electrons generate currents? If not, how does it create magnetic dipole moments?
29 views

Dielectric vs. Ferrite

I am currently taking electricity and magnetism. And I do not understand something, what is the difference between ferrite and dielectric materials. I understand that they each correspond to one of ...
23 views

Re-Radiation from a ferrite rod antenna: Phase relative to the incoming signal

I am working through a problem involving interactions between multiple closely located ferrite bar antennas. I am seeing energy re-radiated from the various antennas coupling into the other ...
13 views

Parameters Affecting Demagnetisation

What parameters will affect how a ferromagnetic material is demagnetised? Assuming that only changing fields will induce demagnetisation (although I suppose I could well be wrong on that one), what ...
44 views

How does one electron or spin see the other in a ferromagnetic material?

QM tells us that only one component of angular momentum is measurable which conventionally taken to be Lz= 1/2. The other two components have an uncertain magnitude and direction and this is usually ...
20 views

Exchange stiffness for HCP

I am studying the exchange interaction, which can be described with the Heisenberg Hamiltonian: $\hat{H} = -\sum_{i,j}J_{ij}\hat{\mathbf{S_i}}\cdot \hat{\mathbf{S_j}}$ In the framework of constant ...
58 views

Difference between domain size and correlation length in ferromagnetic materials?

I am getting confused about different length scales in magnetic materials. I understand that the correlation length for a ferromagnetic materials is defined as <(s(x)−<(s(x))>)(s(y)−<(s(y))>)>...
33 views

Is there a minimum field required in order to start magnetizing an initially unmagnetized ferromagnet?

The question Would a compass with unmagnetized needle work? never seems to have been resolved, due to getting bogged down in a number of sub-issues where different people made seemingly contradictory ...
3k views

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 ...
118 views

Magnetic levitation against Earnshaw's Theorem?

Given six strong magnets, what if we fix three of them to a table in a simple, horizontal, equilateral triangle-like formation (with their north poles sticking up), and the other tree to the points of ...
39 views

What is Magnetic Intensity? [duplicate]

While studying about the magnetic properties of matter, my book defines this vector as $\vec{H}=\dfrac{\vec{B}}{\mu_0}-\vec{M}$ where $B$ is the magnetic field and $M$ is the intensity of ...
23 views

Is the effective magnetic moment defined for substances that follow the Curie-Weiss law?

The effective magnetic moment is defined as follows: \begin{equation} \mu_{eff} = \left(\chi_M \frac{3kT}{N_A\mu_0\mu_B^2}\right)^{\frac{1}{2}} \end{equation} where $\chi_M$ is the molar magnetic ...
54 views

Negative Eigenvalues of the Hessian

I am calculating the eigenvalues of the Hessian for a ferromagnetic system. My energy has the zeeman term, a nearest neighbor exchange term, and a dipole-dipole term. I create the hessian where my ...
30 views

Is voltage basically the measure of the strength (or density) of an electromagnetic field? And does an increase in voltage increase the amperage?

I have been in the process of fully understanding what is generally accepted as truth by the scientific community regarding voltage, watts, and amperage. Most engineers seem to say to simply use the ...
26 views

Does a magnet lose more potential when (passivley) magnetizing another metal?

Does a magnet lose more of it's magnetic potential when (passively) magnetizing a second (ferromagnetic) metal compared with simply being left alone for the same amount of time it took?
48 views

How fast do the magnetic domains align with the external field?

Let say we bring a normal (not super strong) magnet near sort of an unmagnetized iron block. 1) Do the magnetic domains align instantly? Does it make any difference on magnetization strength if we ...