Halbach array

A Halbach array is a special arrangement of permanent magnets that augments the magnetic field on one side of the array while cancelling the field to near zero on the other side. This is achieved by having a spatially rotating pattern of magnetization.
The rotating pattern of permanent magnets (on the front face; on the left, up, right, down) can be continued indefinitely and have the same effect. The effect of this arrangement is roughly similar to many horseshoe magnets placed adjacent to each other, with similar poles touching.

Linear Halbach arrays


this device is also a key component of the Inductrack Maglev train and Inductrack rocket launch system. Wherein the Halbach array repels loops of wire that form the track after the train has been accelerated to a speed able to lift.

The simplest example of a one sided flux magnet is a refrigerator magnet.

illustration of a linear halbach array

Halbach cylinder

A Halbach cylinder is a magnetized cylinder composed of ferromagnetic material producing (in the idealized case) an intense magnetic field confined entirely within the cylinder with zero field outside. The cylinders can also be magnetized such that the magnetic field is entirely outside the cylinder, with zero field inside.
These cylindrical structures are used in devices such as brushless AC motors, magnetic couplings and high field cylinders.

close up of a halbach cylinder
Magnetic flux density graph of a halbach cylinder