What parameters will affect how a ferromagnetic material is demagnetised? Assuming that only changing fields will induce demagnetisation (although I suppose I could well be wrong on that one), what constraints are there on frequency, and how would the magnetic field be able to affect it? Would the size and/or shape of the material help to determine these parameters, or would it be (mostly) magnet design independent.
In school we may use mains electricity to demagnetise a magnet, so that, and the formula for the field due to (and inductance of) a solenoid gives me a ballpark idea of what is possible for a given voltage, and ergo magnetic field, but no concept whatsoever of how this might vary.
Thank you for your time.