How Does Temperature Impact Neodymium Magnet Performance?

[Woodski]

I am interested in the effects of temperature on Permanent Magnets. I understand that Neodymium magnets lose -0.09 ~ -0.13% of Br/°C and can work stably under 80°C for low Hci Neodymium magnets.
However, what happens to them just over this 80°C limit? Do they still have some magnetic strength to attract and repel? If they are cooled, do they retain their full strength or do they loss some strength?

 

[ranger]

Usually the manufacturer will provide a graph, with a BH Curve. Example: http://www.mceproducts.com/_img/materials/N3571.pdf

The Temperature coefficient of Br is a property that describes how the magnetic property changes with temperature. This change is reversible though - the magnetic property returns when the temperature is returned to its original operational point.
But if you don't exceed the knee (shown on the graph), the changes in magnetic property are reversible, otherwise, in most cases it is not.

You will also need to keep in mind something called the curie temperature (Tc). If you exceed this temp, the ferromagnetic material completely loses its magnetic property (and changes in most cases are irreversible).