Most magnets behave the same way: one face is north, the other is south, and the magnetic field spreads out on both sides. A Halbach array breaks that pattern. It is a special arrangement of magnets where the field adds up strongly on one side — and almost disappears on the other.
The trick: rotated magnets
Imagine a row of magnets where each one's magnetization is turned a little compared with its neighbor. After a few segments, the directions have made a full circle. Where the fields point the same way, they join forces; where they point against each other, they cancel out. The result is one “strong side” and one “quiet side” — built from the same magnets that would otherwise produce a field everywhere.
This is not a stronger material. It is pure geometry. Rearranging the same magnets gives you a concentrated field where you need it, and almost no stray field where you do not.
Where you find them
- Motors: the array pushes flux across the tiny air gap where torque is made, so the motor is stronger for its size.
- Maglev tracks: a strong field below the track, near-zero above — safer for passengers and electronics.
- Encoders and sensors: clean, sharp pole patterns give reliable position signals.
- Portable MRI and NMR: bend the array into a ring and the field concentrates inside the bore — no heavy iron needed.
What to remember
A Halbach array costs more than a plain assembly: every segment is magnetized in its own direction, which means extra tooling, and assembly must be done carefully because magnetized segments pull on each other hard. But when a design needs field on one side only, the array often beats a bigger, stronger magnet for the same price.
Read on: how magnetic circuits work → · magnet grades explained →