Eli5 – Why is iron able to become magnetic and aluminium isn’t?


They’re both metals right?

In: 3

Iron, nickel, cobalt, gadolinium, and neodymium are the elements known for making strong magnets.

Matter is made of atoms which are made of Protons, Neutrons, and Electrons.

In most substances, equal numbers of electrons in shells (orbits) spin in opposite directions, which cancels out their magnetism. But in magnetic elements like Iron, Cobalt, and Nickle the electrons in the outer shell spin in the same direction which allows them to carry a magnetic field that accumulates instead of cancelling out. When polarized (when an outside a magnetic field points them all in the same direction) all of these fields from all the atoms accumulate creating a magnet.

Because “metal” isn’t the deciding factor of being a permanent magnet.

The real deciding factor is being able to align all the tiny magnets that are the atoms.

Every atom is a little bit magnetic, but for the most part, all those magnetic fields are in random directions. Except in iron, cobalt, and nickel (and others, but those are the most well known)

For those, there are some processes that align all those magnets together. And just like sticking two full sized magnets together, doing that adds their strength.

Electrons have a property called “spin” which is basically them being tiny little magnets. In most materials the direction the electrons are pointing is random. In certain “ferromagnetic” materials like iron the electrons at the edge of each atom interact with the electrons at the edge of neighboring atoms in such a way that the lowest energy state (which they want to get into) happens when they all point in the same direction. This results in a net magnetic field in the material.

From that explanation it would seem that iron should always be magnetized, but obviously it sometimes isn’t. In that situation the object is actually divided up into tiny regions where the electrons are all aligned, but the different regions aren’t all aligned. Exposing the iron object to a magnetic field (or allowing them align in other ways) gets all the all the regions pointing in the same direction resulting in a net magnetic field.