Hi CapAAVSO@.......

>      I used a row of Wondermagnet's # 13, 1/4 by 1/2"long Neodymium 
> magnets to build a magnetometer. They make a very nice strong 
> compass needle but I heard somewhere they are more temperature 
> sensitive than Alnico magnets we used to use. Does anyone know....

    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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