system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do magnets lose their magnetivity over time?
gpt
There are afew ways a permanent magnet will lose its magnetism.  
   
The most common one is heat.  If you raise a magnet above its "Curie temperature" then its atoms will lose the order that they need to have their magnetic fields aligned. Once the alignment is randomized, virtually every atom has another opposing it and the overall net effect is no magnetic field.   
   
Even low heat will eventually do the same thing, but it can take a very long time. Over time the randomizing effect of the heat will slowly reduce the magnetism.    
    
Another way to demagnetize a permanent magnet is to provide a mechanical shock (whack it with/against something hard).  Like heat, this can de-orient the atomic structure needed to keep the atom's fields aligned.  
    
The third way to do it is to simply apply an opposing magnetic field. The most effective way to do this is to run another magnet along the length of the one you want to demagnetize, over and over.