Magnetism is the force of nature responsible not only for our ability to live on a rock floating through space, but also for major technological achievements that have advanced the human race like never before. Computers rely on them, our livelihood on Earth depends on their principles and our greatest science experiments use the most powerful magnets ever created by man. Were it not for magnetism we simply would not exist, and indeed without discovering the power of this fundamental force of nature, our life on Earth would bear no resemblance to what it is today.
Scientists over the years have employed magnetism in new and innovative ways, delving into realms of particle physics otherwise unexplored, but let’s take a look at how basic magnets are made. It’s fairly common knowledge that objects can be magnetized, making them stick to other magnetic objects, and we know that things such as a fridge or horseshoe magnet always have magnetism. To make permanent magnets like these, substances such as magnetite or neodymium are melted into an alloy and grounded into a powder. This powder can be moulded into any shape by compressing it with hundreds of pounds of pressure. A huge surge of electricity is then passed through it for a brief period of time to permanently magnetize it. Typically, a permanent magnet will lose about one per cent of its magnetism every ten years unless it is subjected to a strong magnetic or electric force, or heated to a high temperature.
To really understand magnets, though, we need to get into exactly what is happening inside these domains. For that, we need to get right down into the atom. Let’s take an iron atom, for example. Electrons circle the nucleus of an atom in cloud-like orbitals, commonly described as rigid shells (although in actuality, their motion is much more random). Each atom has a particular number of shells depending on how many protons and neutrons it has, while within each shell electrons orbit in pairs. Electrons are just like tiny magnets, each one having its own north and south pole. In their pairs, the electrons cancel out one another so there is no overall magnetic force. In an atom such as that of iron, however, this is not the case. There are four electrons that are unpaired, which exert a magnetic force on the atom. When all the atoms are combined together and aligned, as we explained when talking about domains, the iron itself becomes magnetized and attracts other magnetic objects.
So we’ve snapped our magnet, broken it into chunks and subsequently examined the atoms of those tiny chunks. But can we go deeper? The answer to that is yes and no, as we delve into the unknown areas of quantum physics. The underlying principle of magnetism is that in the universe there are four fundamental forces of nature, being gravity, electromagnetism, the weak force and the strong force. Even smaller than atoms and electrons are fundamental particles known as quarks and leptons, which are responsible for these forces. Any force – such as gravity, magnetism, nuclear decay or friction – results from these fundamental forces. A force such as magnetism at this level is ‘thrown’ between particles on what are known as force carrier particles, pushing or pulling the other particles around accordingly.
Unfortunately, however, at this level magnetism enters a completely different realm – that of theoretical physics, entering areas of quantum physics that have not yet been explored in as great detail as particle physics. For now, however, this standard model of physics explains magnetism to a level that can only actually be furthered when science can advance our understanding of quantum physics in the future.
Magnetic atom
Types of magnetism
Ferromagnetism
The strongest magnet in this list, a ferromagne will retain its magnetism unless heated to a temperature known as the Curie point. Cooling it again will return its ferromagnetic properties. Every atom in a ferromagnetic material aligns when a magnetic field is applied. Horseshoe magnets are ferromagnets.
Ferrimagnetism
Ferrimagnets have a constant amount of magnetisation regardless of any applied magnetic field. Natural magnets like lodestones (magnetite) are ferrimagnets, containing iron and oxygen ions. Ferrimagnetism is caused by some of the atoms in a mineral aligning in parallel. It is different from ferromagnetism in that not every atom aligns.
Antiferromagnetism
At low temps, the atoms in an antiferromagnet align in antiparallel. Applying a magnetic field to an antiferromagnet such as chromium will not magnetise it, as the atoms remain opposed. Heating to Neel temp (when paramagnetism can occur) will allow weak magnetism, but further heating will reverse this.
Paramagnetism
Paramagnets, such as magnesium and lithium, have a weak attraction to a magnetic field but don’t retain any magnetism after. It’s caused by at least one unpaired electron in the atoms of a material.
Diamagnetism
Gold, silver and many other elements in the periodic table are diamagnets. Their magnetic loops around the atoms oppose applied fields, so they repel magnets. All materials have some magnetism, but only those with a form of positive magnetism can cancel the negative effects caused by diamagnetism.
What is electromagnet?
One of the four fundamental forces in the universe, electromagnetism results from the interaction of electrically charged particles. Physicist Michael Faraday deduced that a changing magnetic field produces an electric field, while James Maxwell discovered that the reverse is also true: a changing electric field produces a magnetic field. This is the basis of how an electromagnet works.