Forty Rod, there are a few ways to demagnetize. Megnets can be affected by mechanical shock, heat and alternating megnetic fields.
Mechanical shock - lock the knife in a vice and stike th back of the blade several good wacks on the spine of the blade chek the magnetism.
Heat - Heat the knife to beyond the curie point, the problem is it will be about 750 F and will likely effect the temper.
I don't know how much of the blade is magnetic or how big the blade is there is a screwdriver demagnetizer available at a lot of hardware and big box stores. You might be able to get enough of the tip into it.