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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, an intrinsic quantum property, 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 exploited 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), unable to move away or get closer. 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?

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 at the macroscopic scale.

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

The World's Most Powerful Permanent Magnets

This phenomenon of spontaneous alignment is pushed to its extreme in some modern alloys. Magnets based on rare earths, such as those composed 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.

N.B.:
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.

Application Field	Technology / Key Principle	Impact / Performance	Concrete Example
Very High-Speed Transport	Magnetic Levitation (Maglev) & Linear Motors	Speeds > 600 km/h, silence, absence of mechanical friction	SCMaglev line in Japan (Tokyo-Nagoya), Shanghai Transrapid train
Medical Imaging	Magnetic Resonance (MRI) - Superconducting Electromagnets	Magnetic fields of 1.5 to 7 Tesla for non-invasive imaging of soft tissues	Diagnosis of tumors, brain lesions, and muscle pathologies
Nuclear Fusion Energy	Magnetic Confinement of Plasma (Tokamak/Stellarator)	Magnetic fields of several Tesla to confine plasma at > 100 million °C	International ITER project (France), aiming to demonstrate the feasibility of fusion
Energy Storage	Magnetic Flywheels on Magnetic Bearings	Frictionless suspension in a vacuum, efficiency >90%, response in milliseconds	Stabilization of electrical grids, backup power for data centers
Particle Accelerators	Superconducting Electromagnets for Beam Focusing and Deflection	Intense magnetic fields to guide particles at near-light speed	Large Hadron Collider (LHC) at CERN, for fundamental physics research
Environment	High Gradient Magnetic Separation (HGMS)	Extraction of fine metal pollutants or minerals from water and industrial waste	Water depollution, rare metal recycling, mineral purification
Aeronautics & Space	Magnetoplasmadynamic Propulsion (MPD) and Space Protection Magnets	High-impulse electric propulsion for long-duration travel; radiation shielding	Satellite thrusters; magnetic shield concept for manned missions to Mars

Magnets: From the Small Fridge Magnet to Levitation Trains

Magnetism: A Minor Force Capable of Lifting Trains

How to Go from a Negligible Force to a Phenomenal Power?

The World's Most Powerful Permanent Magnets

Magnetism at the Heart of 21st Century Innovations

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