You know that when we approach magnets to an iron nail, the nail will experience an attraction to the magnet. However, not all metals behave in the same way. Some metals are what scientists call ferromagnetic, which means they are permanently magnetized by a magnet. Others are paramagnetic, meaning they are only temporarily magnetized, and others are diamagnetic, meaning they experience a weak repulsion of a magnetic field.
In fact, the complete classification of the magnetic behaviour of materials and their influence on Neodymium Disc Magnet factory and their magnetic properties can be made up of these five main groups:
Diamagnetism. Diamagnetism is a fundamental property of all matter, although it is usually very weak. It is due to the uncooperative behaviour of electrons in orbit when exposed to an applied magnetic field.
Paramagnetism. In this class of materials, some of the atoms or ions in the material have a net magnetic moment due to unpaired electrons in partially filled orbitals. One of the most important atoms with unpaired electrons is iron.
Ferromagnetism. When you think of magnetic materials, you probably think of iron, nickel or magnetite. Unlike paramagnetic materials, the atomic moments in these materials exhibit very strong interactions.
Ferrimagnetism. In ionic compounds, such as oxides, more complex forms of magnetic ordering can occur as a result of the crystalline structure. One type of magnetic order is called ferrimagnetism.
Antiferromagnetism. If moments A and B are exactly the same but opposite, the net moment is zero. This type of magnetic ordering is called antiferromagnetism.
Electrons have a property called a twist, which is a bit like angular momentum (for example, a ball that rotates around its axis), although it is important not to carry this analogy too far, since the twist of electrons is very different from the type of twist movement.
An electron can have a twist of +1/2 or -1/2. Consequently, electrons act a little like small magnets. If two electrons are paired in an orbital, the magnetic fields they produce cancel each other out, and the atom has no net magnetic field.
In this sense, in ferromagnetic materials such as iron, atoms have net magnetic fields and are grouped together with other atoms into a small sub-unit called a domain. A domain can in turn be aligned in any random direction or aligned in the same direction, along with all its neighbors. Magnetic fields are usually not aligned, so a piece of iron metal alone does not have a net magnetic field; the randomly aligned magnetic fields of individual atoms cancel each other out. However, when an external magnetic field is applied, the atoms align with it, so the object is magnetized.
What about diamagnetic materials like copper?
In a diamagnetic field, each atom has paired electrons, so all magnetic fields created by individual electrons are cancelled. When you bring a diamagnetic object close to the magnets, you create small loops of current in the atoms of the material, like miniature wire loops. According to a law of physics called Lenz’s Law, the currents you create run in such a direction that they produce a magnetic field opposite to the one you applied.
A diamagnetic metal like copper not only does not experience attraction to magnets, it actually experiences repulsion. This repulsion is very weak, so unless the magnetic field is very strong, you won’t see it. However, this effect is due to the structure of the metal at the atomic level.
Copper has all the electrons paired in so-called orbitals d, so the atoms in copper do not have net magnetic moments. Diamagnetism is much more common among the elements of the periodic table than ferromagnetism or paramagnetism.
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