What the title said: Are certain brands/types of string more magnetic than others?

The old set of strings (9's, unknown brand since they came with the guitar) on my guitar (with a floating bridge) were attracted to the pickups when enough slack was let into them, but the new set I've just put on (Ernie Ball super slinkies, 9's again) don't react with the pickups at all. To me, this implies that the old strings were magnetically active unlike the new ones.

So in conclusion, does anybody happen to know which string brands are magnetically active? I rather liked being able to drop the tremolo and then bring it back up with a harmonic fretted (which doesn't work with my new strings).
might be that the old strings were on so long that the pickups gave them a magnetic charge. im not sure if thats possible, but it could happen.
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What he said. You are a wise man for not buying into the hype.

ya hear that...he thinks im wise
/\ It does

I play my strings until they die, and by the end, they are all magnetic. Your ernie balls will eventually attract to the magnets, knowing ernie balls, they won't take long (I use 'em. They wear quick but sound great).
^I doubt it. It's a simple matter of some metals being magnetically active (react strongly with magnetic fields), unlike others which are just electrically active (causing an output current from the pickups somehow). Can't remember which off the top of my head, but there're 4 of them in the middle of the periodic table that're very magnetically active.

I'm guessing it's down to the metals in the strings then.
raise your pickups
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