## PSN-L Email List Message

Subject: Re: Passing solar flare geomagnetic shock wave?
From: CapAAVSO@.......
Date: Tue, 13 Jun 2000 22:12:26 EDT

```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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