Coercive field strength is the measurement of a ferromagnetic material’s ability to withstand an external magnetic field without becoming demagnetised. Coercivity is typically measured in oersted or ampere/meter units and is denoted HC.
When comparing magnets, the higher this number, the better the magnet retains its magnetism when exposed to an opposing magnetic field.
There is a difference between the coercive field strength of flux density and the coercive field strength of polarisation. When a magnet is exposed to a demagnetising field strength of bHc, the magnetic flux density in the magnet disappears.
The magnet itself will still be magnetic, but the flux density that the magnet generates is the exact same as the flux density of the demagnistised field, meaning the two cancel each other out.
A magnet will only lose its magnetic polarisation and total magnetism when exposed to a demagnetising field strength of jHc.
Learn more about how the strength of a magnet is measured here.
