Magnetic losses due to shock 2

[mprice]

I would like to know if there is any data available for the magnetic losses caused by shock loading a small SmCo magnet. I have a magnet which is used in conjuction with a Hall effect sensor to make a displacement measurement of a lever. The magnet is subject to approx 12g shock which is irregular but will happen about 1000 times per year. Is this likely to give large magnetic losses?

 

[drdick]

The effect of shock would depend on the magnet's resistance to demagnetization, i.e. it's coercivity (Hc) and magnetic length. Hc for SMCo is relatively high, but thin (L/D=<.1) magnets have weak domains at corners/edges that can be reversed by external energy sources.
If there is potential for this to occur, then the magnets should be stabilized thermally. The idea is to introduce enough external energy to allow weak domains to reverse before they see an equivalent amount of mechanical energy. Since that would be difficult to calculate, a thermal soak at 100°C would at least ease your mind. If L/D > .2 there is little potential for problems with shock that does not physically break the magnet.