Magnetism is a fundamental force of nature created by moving electric charges, which allows materials to attract or repel each other across a magnetic field. At its most basic level, all matter possesses some degree of magnetism because every atom contains electrons in motion. This microscopic movement generates tiny magnetic moments, essentially making every electron a miniature magnet. The familiar effects of a magnet, such as the strong pull felt on a refrigerator door, are the result of these countless atomic forces combining on a macroscopic scale. The premise that all metals are magnetic is inaccurate, however, as only a small number of metals exhibit the strong magnetic behavior typically associated with the term.
Correcting the Premise: Not All Metals Are Magnetic
The idea that all metals are magnetic is a common misconception, often stemming from the powerful attraction demonstrated by metals like iron. Magnetism is not a simple on-or-off property but exists on a broad spectrum, classifying how a material responds to an external magnetic field. Only a small group of elements, including iron, nickel, and cobalt, display the strong form of attraction that the average person recognizes as magnetic.
Most other metals, such as aluminum, copper, and gold, are typically described as non-magnetic because their response to a field is incredibly weak. Aluminum, for example, is technically attracted to a magnet, but the force is so slight it is undetectable without specialized laboratory equipment. Copper and gold, conversely, are actually weakly repelled by a magnetic field.
How Electron Structure Creates Magnetism
The origin of a metal’s magnetic properties lies entirely in the behavior of its electrons, specifically their intrinsic spin. Every electron acts as a tiny spinning charge, which generates a small magnetic field, known as a magnetic moment. The overall magnetism of an atom depends on how these individual magnetic moments add up or cancel each other out.
Electrons generally exist in pairs within an atom’s orbitals, with one electron spinning in the opposite direction to its partner. This opposite spin causes their magnetic moments to perfectly cancel each other, resulting in no net magnetic field for that pair. Atoms with all their electrons paired are therefore considered non-magnetic.
Magnetism arises only in atoms that contain unpaired electrons, whose magnetic moments are not canceled out and can therefore contribute to a net magnetic moment for the entire atom. The presence of these unpaired electrons is the first requirement for a metal to be magnetic. Elements like iron, nickel, and cobalt have multiple unpaired electrons in their outer shells, giving each atom a relatively strong, permanent magnetic moment.
For a material to exhibit the strong magnetism associated with a permanent magnet, a second condition must be met: the alignment of magnetic domains. These domains are microscopic regions where the magnetic moments of countless individual atoms are spontaneously aligned in the same direction. In an unmagnetized ferromagnetic metal, the magnetic domains are randomly oriented, causing their magnetic fields to cancel each other out on a larger scale.
When an external magnet is brought close, the forces overcome this randomness and cause the domains to rotate and align with the external field. This collective alignment creates a powerful, unified magnetic field that extends outside the material. When the external field is removed, certain materials, known as “hard” ferromagnets, retain this domain alignment, which is how permanent magnets are made.
Understanding the Three Main Types of Magnetism
The behavior of electrons and their magnetic moments leads to three primary classifications for how metals interact with a magnetic field.
Ferromagnetism
The strongest and most familiar type is ferromagnetism, which is characteristic of iron, nickel, and cobalt. Ferromagnetic materials are strongly attracted to magnets and can be permanently magnetized.
Paramagnetism
This occurs in metals such as aluminum and platinum, which contain unpaired electrons but do not form the permanently aligned magnetic domains of ferromagnets. These materials are only very weakly attracted to a magnetic field, and their magnetic alignment disappears the moment the external field is removed. The attraction is millions of times weaker than ferromagnetism.
Diamagnetism
This property is present in all materials, but most apparent in those with only paired electrons, like copper and gold. In diamagnetic materials, the external magnetic field slightly shifts the orbits of the electrons, which in turn induces a very weak magnetic moment that opposes the applied field. This opposition results in a slight repulsion from the magnet, a force so faint that it requires highly sensitive instruments to detect.