I have found a useful source of magnets in the McMaster Supply
 catalog (www.mcmaster.com; 3000 page catalog 630-833-0399).
 They have two pages of Alnico-5 and Alnico-8, and another two
 pages of rare earth magnets and ceramic multipoles. I am using a 
 bonded neodymium ring magnet for a new feedback transducer.
 I think that their offering is more complete and consistent 
 than Edmund Scientific. THey have some rather large offerings.

 Also, the magazine "Motion Control" (www.isa.org)) recently had a two 
 part article on the characteristics and manufacture of NdFeB (neodymium)
 magnets in their June and July issues. The June issue goes into details of
 linear motors or voice coil motors, which seismometer feedback transducers
 are, or moving coil velocity sensors are the reverse of, using either 
 cylindrical (disk) or ring magnets. There is a table of field strength 
 B vs coercivity H for various alloys and fabrication methods. It clearly
 shows the up to 5 to 1 improvement of neo methods over Alnico or ceramic
 ferrite, with pricey Samarium-Cobalt in the middle.

 Regards,
 Sean-Thomas
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