It is a fact that permanent magnet loose its magnetic properties on heating. I want to weaken the magnet by heating. is it possible? if so will any of you provide me details. do you have any graph that can help.

Regards
Aziz Rahman

 

It looses it's magnetic strength when heated above its curie temperature. For how much it depends on the magnet material and grade.

Example:
NdFeB (steep loss with rising temp)
Alnico (Little change with temp)

I have a chart for several materials, but I do not know how to post a pict yet. (Sorry)

You may be able to find info on the web at magnet manufactured websites:

http://www.kjmagnetics.com/bhcurves.asp

If you are unsure of you magnet material, you may have better luck changing the magnetic circut. (ie. changing the flux path by adding a piece of iron, or changing the gap)

Hope that helps.