# Anyone processed Platinum-Cobalt Permanent Magnets?



## hyderconsulting (Jun 9, 2007)

Has anyone ever processed Platinum-Cobalt Permanent Magnets? As I understand these magnets were used in the first hearing aids made, the first electric watches and in magnetic phonograph cartridges. These items date back along 1965 thru the early 70's I believe. The magnets are 23% by weight cobalt and the rest platinum. My book reference, ASM International Metals Handbook, Vol. 2, Tenth Ed., also states they were used in rotors in miniature motors, gyro bearings, and platinum-cobalt films for use in digital magnetooptico recording. I had thought about buying a few of the phonograph cartridges on ebay to see what is in them for they do turn up there at times. Regards, Chris.


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## Charlena (Jun 23, 2007)

and the out come! thanks!


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## raju-smg (Jul 12, 2013)

yes- i have processed platinum cobalt magnet. it can be made in any sizes

regards
govindaraju
India


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## pgms4me (Jul 12, 2013)

Thanks for this post. I have old magnetic cartridges and some specialized small motors of that era. I will take some apart and see if i can test them. Cobalt is an easy metal to test for,but i think many magnets of that era used cobalt as one of the alloy metals so maybe the best way is to dissolve a sample in aqua regia and then test with stannous


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## rucito (Jul 15, 2013)

http://www.google.com/patents/US4983230

The coercivity of magnetic alloys formed from platinum, cobalt, and boron is enhanced by incorporating from 12 to 14 percent of boron together with amounts of platinum and cobalt such that the ratio of platinum to cobalt is from 0.90 to 1.2. The magnetic alloy is formed by rapid solidification of a homogeneous melt, and the solidified casting is heat treated to improve microstructure and increase coercivity.


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