With increasing heat, the magnet will gradually lose magnetization until a certain temperature (called the Curie temperature) at which the magnetization goes away entirely.In addition to this effect, the domains of the magnet will have a greater chance of changing orientation, further weakening the overall effect.
I like to share this heat equation with you all through my article.
As for specific temperature of 350 degrees, we can say that the effect will decrease ( and possibly vanish -- it depends on the material your magnet is made of ) while the magnet is maintained at that temperature and it will probably be weaker when the magnet is cooled back down to room temperature.There is a dependence of the spontaneous magnetic moment of a ferromagnetic what we call magnetic force. As the temperature decreases the spontaneous magnetic moment increases.
The magnet is warmed up, the spontaneous moment decreases until it reaches the Curie temperature, where it goes to zero. This is not a linear effect, and there is a maximum value for the spontaneous moment that would be reached as the temperature approaches absolute zero.Effect of HeatingThe magnetic moment of a ferromagnetic will also be affected by other factors, most notably an external magnetic field. The spontaneous magnetic moment exists independently in an external magnetic field.
A permanent magnet like the one you are using, the material is inherently magnetic and that will not go away as long as it is not heated.However, not all portions of the magnet must have the same magnetic field direction. These magnets are divided into domains. To get the material to behave as a magnet, one domain must be increased in size, so that it dominates. An unmagnified chunk just has equally sized domains with fields pointing in every direction. To magnetize an object like this, you put it into a large magnetic field and wait.The domains will slowly redistribute themselves by thermal fluctuations.