Ferromagnetism, what's happening in cylindrical magnets?

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SUMMARY

The discussion centers on the simulation of ferromagnetism in cylindrical magnets using COMSOL Multiphysics. It is established that the magnetic flux density (B) becomes more uniform as the aspect ratio (length/diameter) of the magnet increases. Specifically, a rod with a length of 2mm and a diameter of 6mm (aspect ratio 1/3) exhibits a strong magnetic field at the periphery and a weaker field along the central axis. The findings highlight the importance of aspect ratio in determining the uniformity of magnetic fields in cylindrical magnets.

PREREQUISITES
  • Understanding of ferromagnetism principles
  • Familiarity with magnetic flux density (B)
  • Knowledge of COMSOL Multiphysics simulation software
  • Basic concepts of aspect ratio in geometry
NEXT STEPS
  • Explore COMSOL Multiphysics tutorials for simulating magnetic fields
  • Study the mathematical models governing magnetic flux density in ferromagnetic materials
  • Research the effects of aspect ratio on magnetic field uniformity
  • Learn about physical laws related to magnetism, such as Ampère's Law and Gauss's Law
USEFUL FOR

This discussion is beneficial for physicists, engineers, and researchers interested in magnetism, particularly those working with simulations of ferromagnetic materials and cylindrical magnets.

soljiang
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I've a question on ferromagnetism. I've been trying to simulating the field around a rod shape magnet, cylindrical in shape and N on one end and S on the other. I just wonder if one would expect the the B, the magnetic flux density, to be uniform in magnet. I used comsol to simulate and get different results for rods with different aspect radio.
Basically the simulation demonstrates that the higher the aspect ratio (length/diameter), the more uniform the B is in the magnets. When the length is 2mm and the diameter is 6mm (aspect ratio 1/3), then the B is very strong at the periphery of the cylinder and weaker in the middle along the central axis.
I'd really appreciate if someone could offer me some help on mathematical and physical explanation, such as physical laws and maths formula. Thank you very much!


Charles
 

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Here's a fourth picture that shows the uniformity of the B when aspect ratio is high.
 

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