Does heating magnetic materials affects it's magnetism?

Yes, heating magnetic materials changes magnetic properties. The magnetic susceptibility of ferromagnetic materials decreases with temperature upto a point called the Curie temperature after which they behave like paramagnetic materials. Other kinds of materials undergo changes with temperature as well. read more

Yes. There are three types of magnetic substances: Diamagnetic: Its magnetic properties do not depend on temperature Paramagnetic: Depends inversely with temperature Ferromagnetic: Depends almost inversely (but not exactly) with temperature. read more

When exposed to extreme temperatures, however, this balance is destabilized; magnetic properties are then affected. While cold strengthens magnets, heat can result in the loss of magnetic properties. In other words, too much heat can completely ruin a magnet. read more