How to predict a magnet's field strength?

[downtownjapan]

Hi,

I am interested in making my own (weak) magnets exposing some ferrous metal to the magnetic field of an electromagnet, but this is theoretical rather than something I am able to actually do right now. I am wondering if there are any formulas that can help calculate/estimate the resulting field strength of the permanent magnet being created. I am guessing the key factors are the strength of the field the ferrous material is exposed to, and the time the material is exposed - but I am not sure how the material qualities might affect the process. Are there any formulas or even rules of thumb that I can use to estimate the permanent magnet's field strength?

Thanks,
Eddie

 

[UltrafastPED]

Are you planning something like this guy does?

http://www.instructables.com/id/Permanent-Magnets/

If you heat a magnetic material above its "Curie temperature" it will lose any existing magnetization. So when it is in this condition you can expose it to a strong magnetic field (e.g., via an electromagnet such as a Helmholtz coil), and slowly lower the temperature.

See http://en.wikipedia.org/wiki/Curie_temperature
and http://en.wikipedia.org/wiki/Helmholtz_coil

You can make everything that you need.