What makes magnetic metals magnetic?



What makes magnetic metals magnetic?

In: Physics


The metals have a load of things called electrons in them.

Electrons (and some other stuff) have a property called “spin,” which is one of those weird quantum mechanics things. Spin isn’t a kind of movement, but (mathematically) acts a lot like spinning.

One of the ways it acts like actual spinning is that it causes a tiny magnetic field (due to it being like an accelerating or moving charge).

An electron can have two different kinds of spin, sometimes called “up” and “down” or “1/2” and “-1/2”, which if spin was like actual spinning would correspond to the two directions something can spin (clockwise or anticlockwise) – but because it isn’t spinning, don’t.

Which direction the tiny magnetic field goes depends on the spin. And normally electrons will pair up, with one of each spin, and their magnetic fields will cancel out (at large enough distances away).

But in some metals the electrons are arranged in specific patterns, where their spins interact and sort of “line up”, and so their magnetic fields add together, creating a large scale magnetic field. Some metals form these arrangements naturally and are fixed (“hard” magnets), and in some metals you can force the electrons to line up by putting the metal in a strong magnetic field, but then you can also knock them out of alignment (“soft” magnets).