What’s Pauli's principle?

Pauli’s principle, also known as the Pauli ban or the Paulian exclusion principle, was discovered in 1924 by physicist Wolfgang Ernst Pauli, who almost 20 years later also received the Nobel Prize for his work. Generally speaking, according to Pauli's principle, two electrons in an atom should never have exactly the same state. This description makes it clear why it is also called a prohibition or exclusion principle. To explain and understand this in more detail, we must first clarify some basic concepts.

Explanations of terms related to Pauli’s principle

The state of an electron is measured with the so-called quantum numbers. These are four different physical quantities that represent the properties of the electron: the energy - abbreviated with "n", the angular momentum "l", the orientation of this angular momentum "m", and the orientation of the Electrospins "s". In addition, there is the abbreviation "sm" which means the alignment of the electrospin. Consequently, these five variables for the motion properties of the electron appear in an equation and according to Pauli's principle, they should never be the same.

However, there is a limitation. This principle does not apply simply to all electrons, but only to those whose spin is not an integer. These electrons are called fermions. We call all particles with whole turns to which the exclusion principle we call bosons does not apply. The space within an atom in which electrons are found and cannot remain at the same time if they are not integers and have the same arrangement is called orbital. These are the most important terms to understand Pauli's principle.

Pauli's principle in relation to ferromagnetism.

Ferromagnetism eventually occurs through the interaction of electron exchange in a solid. This can also be explained using Pauli's principle. How? Let's see that below:

As we have already clarified in other publications in our blog, magnetism occurs precisely because electrospins should not have a different direction of rotation. Now, Pauli's principle prohibits within the magnet that the spins on adjacent electrons are different, a force arises between these electrons, which places the spins in parallel and stabilizes them. This is where the exchange interaction occurs. This is so strong that, as we have already clarified, a ferromagnetic magnetized substance does not lose its magnetic force so easily, even if the external influence is disconnected. With electromagnets this is the exact opposite.

If you would like more information on the connection between Pauli's principle and ferromagnetism or have other questions, you can contact our experts team at any time. We will be happy to advise you without obligation and offer more detailed information