How to prove SmCo magnets can work on 550celsius degree ?

How to prove  SmCo magnets can work on 550celsius degree?  Heating test is  an effective method. 
In general , we can supply demag curve(as curve 1 amd curve 2) of magnet on different temperature  to sure it can work on certain temperature,but maxmium temperture is no more 200 celsius degree . When working temperature more than 200 celsius degree , the effective way  is check the irreversible flux loss before and after heating test.  
the detailed test step is followed :
1.  Full magnetized test samples D10x10 , test the magnetic flux1. 
2.  Place the samples on to the iron plate and put the plate into heating furnace. 
3.  Heating magnets samples on to 550 Celsius Degree and keep 550 Celsius degree  for 1 or 2 hours . 
4.  Stop heating and open the furnace door and until the temperature down to room temperature.
5.  Test magnetic flux2  , and calculate the flux loss base on folllowing format : 
     Flux loss =  (flux2- flux 1)/flux1*100%   
6.  Flux loss is about - 5% , smco magnets is proved ok for using in 550 Celsius degree.