Part of the show Science Question and Answer - New Horizons Mission
Andrew, in Essex. asked:
What are magnets made out of and how are they made?
Magnets are very useful things: you can stick things to fridges with them and they're very important in things like hard disk drives in your computer. You can even make levitating trains with them. But how do you make a magnet?
Inside a metal like iron there are lots of tiny little magnets [called dipoles]; to start off with, they're all pointing in different directions. It's like if you had a load of magnets inside a big bucket: they'd all be pointing in a random way. What you need to do to make them into a magnet is to line up all those tiny magnets [dipoles]. The way you do it is to heat up the material, which allows all the mini magnets to move around. You then put a big magnetic field around it. This causes all the little magnet dipoles to line up, as you may have seen compasses do in a magnetic field. If you then cool down the material in that magnetic field, the dipoles will all be lined up and you'll have what you think of as a permanent magnet.
Of the elements in the periodic table, iron, nickel, aluminium and cobolt can be made into magnets. These latter elements are referred to as al-ni-co. They have what is called a high coercivity, which means that, once magnetised, they have a strong tendency to remain magnetic.
Some of the rare Earth elements are also used to make magnets. These include neodymium and samarium.