On Fri, 28 Mar 2003 JordanVw@AOL.COM wrote:

> ok..ill bite..what the hell is the diff between a "rare earth magnet" (sounds
> like something you would pick up at a phish concert or a Dead shop) and a
> regular magnet?

There are several types of magnets.  The oldest and simplest is a piece of
iron that's been magnetized.  These are cheap and come in a lot of
different shapes and sizes, but they're weak and can easily be
demagnetized by heat, impact, and age.

Rare earth magnets use special alloys with (relatively) expensive "rare
earth" minerals.  They're generally much stronger and don't demagnetize
easily.  They come in dozens of formulations with different properties.

I have one example that came out of a hard disk head positioner mechanism.
The magnet is about 1/8" thick, with a 1/4" metal pole piece attached, and
around the size of a quarter.  It's so strong it's nearly impossible to
pull off a steel surface with your fingers.  It will attract dollar bills
(due to the magnetic ink) and Canadian coins (due to the nickel content.)

David Brodbeck, N8SRE
'82 Diesel Westfalia
'94 Honda Civic Si