Paramagnetism — Definition

Definition

Imagine a tiny compass needle inside every atom of a material. In some materials, called paramagnetic materials, these tiny compass needles (which we call atomic magnetic moments) are usually pointing in all sorts of random directions.

This randomness is caused by the constant jiggling and vibrating of atoms due to heat (thermal energy). Because they're all pointing randomly, their effects cancel each other out, and the material doesn't show any overall magnetism on its own.

It's like having a crowd of people all facing different directions – there's no overall direction for the crowd.

Now, what happens if you bring a strong magnet near this paramagnetic material? The external magnet acts like a strong wind, trying to push all those tiny compass needles to point in the same direction as the external magnet's field.

Some of them will indeed turn and align themselves with the external field. This alignment isn't perfect, because the thermal jiggling is still trying to randomize them, but enough of them align to create a weak, temporary magnetic field *inside* the paramagnetic material, pointing in the same direction as the external field.

This is why paramagnetic materials are weakly attracted to magnets.

Crucially, this attraction is only temporary. The moment you remove the external magnet, the thermal jiggling quickly takes over again, and all those tiny compass needles go back to their random orientations. The material loses its induced magnetism almost immediately. This is a key difference from ferromagnetic materials, which can become permanently magnetized.

The reason these materials have these 'tiny compass needles' in the first place is due to the presence of unpaired electrons in their atoms or molecules. Electrons, besides orbiting the nucleus, also spin, and this spin creates a tiny magnetic field.

If an atom has an equal number of electrons spinning in opposite directions, their magnetic fields cancel out. But if there's an unpaired electron, its magnetic field isn't cancelled, and that's what gives the atom its net magnetic moment.

So, in essence, paramagnetism is the weak, temporary magnetic response of materials containing unpaired electrons, which align partially with an external magnetic field but lose this alignment once the field is removed.