Ceramic Magnets and their durability in temperature fluctuations

[bluerayz]

I work in the Aggregate industry and we use ceramic magnets to pull ferrous materials out of the feed of Aggregate materials passing by on a conveyor belt.
So i have a basic knowledge about how they work, but my technical knowledge about magents is extremely lacking.

Wondering if anyone would have any theories as to why a ceramic permanent magnet would lose its strength working in a place with extremely cold temparatures? I.E. -40° C.
I know that permanent magnets become stronger when they are put in extremely cold temps, but I'm wondering if going from -40 to +20 every 24 hours for months in a row might gradually decrease the strength over time??

Any thoughts would be helpful. Thanx in advance.

 

[nasu]

What kind of ceramic? Is it a ferrite?

 

[bluerayz]

It is Ferrite.

 

[nasu]

The values of the coercive field of some ferrites may decrease significantly at low temperature. This will make the magnet more sensitive to weak external fields, which may demagnetize it or reduce its magnetization.