A Halbach magnet array is a special arrangement of permanent magnets that makes the magnetic field on one side of the array stronger, while canceling the field to near zero on the other side. This is very different from the magnetic field around a single magnet. With a single magnet, you have an equal strength magnetic field on either side of the magnet.

The effect was initially discovered by John C. Mallinson in 1973, and these "one-sided flux" structures were initially described by him as a curiosity . In the 1980s, physicist Klaus Halbach independently invented the Halbach array to focus particle beams, electrons and lasers.

Common Halbach magnet arrays are linear and cylindrical. Linear array structures are mainly used in linear motors, such as maglev train; Cylindrical array structure is mainly used in permanent magnet motors, such as the blood flow pump motor in the cardiac blood propulsion system. The focusing magnetic field of the cylindrical array structure is also suitable for traveling wave tubes for communication satellites, radar microwave magnetrons, etc.