How to model demagnetization of a permanent magnet due to high fields

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I am trying to model the magnetic field, magnetic flux density, and magnetization of a cuboid shaped neodymium magnet (N42 material), in a magnetostatic situation.

I have made a simple model with a block for the magnet and a block for an air box around it, and am using the magnetic fields, no currents module. The magnet has been set up with a North and South pole.

So far, the magnet produces the expected magnetic field distribution, and shows the expected magnetization inside the magnet of M = Br/mu0 = 1.31T/mu0 = 1e6 A/m (see attached picture).

Now I would like to see what happens as a larger and larger external magnetic field is applied. I know for such magnets that as the field strength H is increased beyond the coercivity then the magnet should become demagnetized, and I would expect the magnetization to self-consitently reduce in the model. I know for N42 magnets that this should happen around reaching a field of ~1000 kA/m. I would like to see this reproduced in the simulation.

How can I verify that such an effect is present in the model?

(for context, my goal with this model is to place many strong permanent magnets close to each other. This is expected to generate strong magnetic fields which exceeds the coercivity in some regions. And so I would like the model to account for the reduced magnetization of some parts of the magnets).



2 Replies Last Post Oct 30, 2023, 5:38 a.m. EDT
Edgar J. Kaiser Certified Consultant

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Posted: 6 months ago Oct 27, 2023, 11:43 a.m. EDT

Fedja,

you would need to use a hysteretic magnetization model, such as Jiles-Atherton in the magnet. JA is available in COMSOL and you need to acquire the respective parameters for the magnet material.

Cheers Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Fedja, you would need to use a hysteretic magnetization model, such as Jiles-Atherton in the magnet. JA is available in COMSOL and you need to acquire the respective parameters for the magnet material. Cheers Edgar

Lars Gregersen COMSOL Employee

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Posted: 6 months ago Oct 30, 2023, 5:38 a.m. EDT

There is a nice app that shows how to make it for a super conductor: https://www.comsol.com/blogs/solving-the-superconductor-teaching-challenge-with-apps/

It has some nice animations. Perhaps it can give you some ideas.

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Lars Gregersen
Comsol Denmark
There is a nice app that shows how to make it for a super conductor: https://www.comsol.com/blogs/solving-the-superconductor-teaching-challenge-with-apps/ It has some nice animations. Perhaps it can give you some ideas.

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