Remove the cartridge and see if you still have hum. If you don't that means you ruined it. A demagnetizer is the worst tool to use they cause nothing but problems.
Turntable hum problem after demagnetizing
I borrowed a friend's Benz Aesthetix demagnetizer to try out. (Oracle Delphi V, Wilson Benesch ACT 0.5, Benz LP-S, Cardas Golden Cross phono cable, Pass Labs XONO phono preamp). After using it, I now have a huge hum that wasn't there before. There also is static if I clean a record with my carbon fiber brush or touch it to the stylus. Also when I touch the tonearm the hum increases. What is going on??? Any help would be appreciated.