Last updated: February 22, 2026

Magnets: From the Small Fridge Magnet to Levitation Trains

Magnetism: a minor force capable of lifting trains

Magnetism is a manifestation of electromagnetism, one of the four fundamental interactions of nature. It arises from the movement of electric charges and, more specifically, from the spin of electrons—a quantum property intrinsic to electrons, just like mass or charge.

At first glance, magnetism seems to be a minor force: a small fridge magnet struggles to hold a few sheets of paper. Yet, this same physical force is harnessed by Maglev trains to levitate and guide themselves without contact. An active control system keeps them at an extremely precise distance from the rails (between 10 and 15 mm), preventing them from moving closer or farther away. The train is literally "glued" at this height by an intense magnetic field. However, the absence of mechanical friction allows an independent electromagnetic motor to accelerate them to over 600 km/h.

How to go from a negligible force to a phenomenal power?

The microscopic origin of magnetism: electron spin

At the most fundamental level, magnetism originates from the spin and electrostatic repulsion of electrons. Each electron behaves like a tiny bipolar magnet (with a North and a South pole). In most materials, these micro-magnets (spins) are randomly oriented. Their magnetic effects cancel each other out, so the material exhibits no net magnetic field on a macroscopic scale.

Ferromagnetic materials and Weiss domains

In ferromagnetic materials (such as iron, cobalt, or nickel), electrostatic movements favor a parallel alignment of electron spins. This alignment of billions of tiny electronic "compasses" forms microscopic magnetic "islands" (Weiss domains). Each island is like a large ship with thousands of rowers all rowing perfectly in the same direction (the spins are aligned). When most of these islands align in the same direction, the material becomes a very strong permanent magnet.

Note:
Weiss domains, named after the French physicist Pierre-Ernest Weiss (1865-1940), are microscopic regions (typically 10 to 100 micrometers) within a ferromagnetic material where all electron spins are naturally aligned in the same direction, even in the absence of an external field.

The world's most powerful permanent magnets

This phenomenon of spontaneous alignment is taken to its extreme in certain modern alloys. Rare-earth magnets, such as those made of neodymium, iron, and boron (NdFeB), exploit a particular crystalline structure. This structure strengthens the exchange interaction and "freezes" the alignment of spins, creating materials with extreme properties: record saturation magnetization and resistance to demagnetization. This is what makes NdFeB the most powerful permanent magnet.

Why the difference in scale between a small fridge magnet and a Maglev train?

The key lies in the difference between spontaneous magnetization and the magnetic field produced. In a small fridge magnet, magnetization (the alignment of electron spins) is already strong on a microscopic scale, but the volume of magnetic material is very small and the poles are close together, which limits the range and intensity of the field felt at a distance.

In a Maglev train, a simple permanent magnet of the same size is not used: either superconducting electromagnets (in the electrodynamic system) or a succession of very high-performance permanent magnets (neodymium) combined with active coils are used. The trick is, on the one hand, to multiply the active volume (kilometers of rails and entire carriages of magnets) and, on the other hand, to channel and amplify the flux via soft iron magnetic circuits. Above all, in the case of superconducting electromagnets, phenomenal current densities (over 100 A/mm²) are achieved without Joule effect losses, producing magnetic fields of several teslas—thousands of times more intense than that of a small fridge magnet.

Thus, the "minor" force at the gram scale becomes colossal at the ton scale, through the accumulation of magnetization, current, and interaction surface.

Note:
The first observations of magnetism date back to ancient China, where magnetite was used as early as the 4th century BCE for orientation. In the 19th century, the work of Hans Christian Ørsted (1777-1851) revealed the link between electric current and magnetic field. This discovery was formalized by James Clerk Maxwell (1831-1879), whose equations unify electricity and magnetism.