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 constraints are there on frequency, and how would the magnetic field be able to affect it? Would the size and/or shape of the material help to determine these parameters, or would it be (mostly) magnet design independent.

In school we may use mains electricity to demagnetise a magnet, so that, and the formula for the field due to (and inductance of) a solenoid gives me a ballpark idea of what is possible for a given voltage, and ergo magnetic field, but no concept whatsoever of how this might vary.

Thank you for your time.

  • $\begingroup$ Have you searched for material on DEGAUSSING or DEMAGNETIZATION ENERGY on the web? $\endgroup$ – niels nielsen Feb 9 at 1:13
  • $\begingroup$ The stuff I've found thus far which mentions 'demagnetising energy' has all been papers behind a paywall, and 'degaussing' as a process tends to pull up references to the application of the technique, rather than the theory behind it, or anything on the parameters affecting it. $\endgroup$ – DoublyNegative Feb 9 at 17:22
  • $\begingroup$ Keep looking, there is useful stuff to be found. physics textbooks also deal with this. try websites for companies that sell magnetic materials too. $\endgroup$ – niels nielsen Feb 9 at 18:22
  • $\begingroup$ Mains frequency is fine, higher frequencies do not penetrate very far in metals. Move the degaussing coil away before switching it off. $\endgroup$ – Pieter Feb 9 at 22:24
  • $\begingroup$ So should I be considering the magnetic skin-depth of the metal, then, when looking at how far the field propagates. And even given that, in my research I still haven't found factors determining how much, for a given field and/or frequency, it demagnetises, although I can qualitatively understand that the penetration distance would be related to it (if there's - approximately - no field, I would expect no change, that's logical). $\endgroup$ – DoublyNegative Feb 10 at 11:23

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