What factor reduce the magnetization of a perninant magnet
Heat will adversely affect a magnet.
In addition to heating the magnet (mentioned above), I think that banging the magnet with a sledge hammer (without breaking the magnet into pieces) will reduce the magnetization by breaking up some of the magnetic domains in the magnetized metal or ceramic material.
Spilling mistake with predictive writing (T9) on mobile :) permanent
Separate names with a comma.