In a message dated 6/13/00 7:15:36 PM Eastern Daylight Time, 
ChrisAtUpw@....... writes:

<< .Funny that you should ask about temperature coefficients of magnets. I 
 looked last month :-
     
     Ceramic magnets have a temperature coefficient of -0.18 to -0.2% per 
 degree C. 
 
     Radio Shack claim that the temperature coefficient of their ceramic 
 magnets is -0.16%/degree C. They also quote 2250 Gauss. 
 
      Nd-Fe-B permanent magnets have a temperature coefficient of -.09% to 
 -.13% per degree C.
 
     Samarium Cobalt magnets have a temperature coefficient of -.03% to -.04% 
 per degree C.
  
     Alnico has the lowest temperature coefficient of commercial magnetic 
 material. However there are various 'grades' of  Alnico. Alnico 5 at has a 
 temperature coefficient 0.023%. Alnico 8H has a temperature coefficient of 
 0.012%, but it may only be available in in large quantity.
 
     I haven't yet got a figure for Ticonal. Anyone ..?
  
     See :-
  
     Bunting Magnetics for ALNICO 8HE on their website 
     www.buntingmagnetics.com 
 
     Arnold Engineering Company on   
 http://www.grouparnold.com/products/alnico/pdf/sacatrev.pdf 
 
     Regards,
 
     Chris Chapman >>
        
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Hi Chris,
    Thanks for the very useful information about the temperature sensitivity 
of various magnets. The spring constant of the torsion wire that suspends the 
magnets is also temperature sensitive like the magnets but I don't know how 
their magnitudes compare or if they add (it would be nice if they canceled 
!!). Can somebody figure this one out? A magnet 1/4 inch diameter and 4 
inches long is suspended on a 15-inch length of high carbon steel music wire 
..008 inches in diameter. The torsion wire is twisted so the magnet points 
east and west instead of north and south as the magnet would like to do. 
Which direction will a temperature change rotate the magnet and how much is 
due to the magnet and how much to the torsion wire?
Regards,
Cap  
 
 

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