The magnet I ordered has a Br spec of 12.4 kG – why is the flux density only measuring 3.0 kG?
This is best explained through referencing the permanent magnet characteristic of permeance coefficient, which is strictly determined by geometry. In general, longer magnets have greater permeance coefficients. Additionally, a magnet with a higher permeance coefficient functions at a higher operating point. Now, imagine stretching a magnet so that its magnetic length is infinite. Per the previous few sentences, this would result in a magnet with the largest possible permeance coefficient and, consequently, the highest possible operating point. This is the only configuration where a magnet operates at Br. Any other geometric configuration will operate at some point less than this. Since practical magnets have discrete lengths less than infinity, they fall victim to this geometric constraint and operate at levels lower than the Br value. Further, a magnet’s Br value is not an indication of the field density seen outside of the magnet. It is the induced field, inside of the magnet, which
