Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: demagnetizing neodymium magnets

Learn more physics!

Most recent answer: 04/26/2016
Q:
I am getting into dismantling of hard drives, which will give a lot of neudymium magnet scrap. This magnet scrap will go to a recycler in Japan, who only accept such scrap , if their magnetic force is removed.I should be producing 4000 - 5000 pieces of such magnets everyday. What sort of an inductor can i use to remove the magnetic force from this magnet scrap?Are there any other ways to remove the magnetic force from neudymium magnets?
- Himanshu Kawatra (age 26)
Panipat
A:

It takes a big ac field to demagnetize those magnets at room temperature. You can demagnetize them by heating them to the Curie temperature, but that may be inconveniently high, e.g. 350°C. Another option is to heat to some lower temperature and apply a smaller ac field than would be needed at room temperature. Some of the specifications for temperatures and fields needed can be found on this commercial site:
 https://www.kjmagnetics.com/blog.asp?p=temperature-and-neodymium-magnets.

By the way, I've found that electric toothbrush heads contain strong magnets, probably neodymium-based. I wonder if it would be practical to recycle those. I use them on my refrigerator door.

Mike W.


(published on 04/26/2016)

Follow-up on this answer.