All three shape a magnetic field on purpose, but they do it differently and suit different jobs.
A multipole magnet usually means a single magnet magnetized with several alternating north and south poles, such as a ring with six or twelve poles. These are standard in motors, encoders and Hall-effect sensors. The pattern is regular and comes from a magnetizing fixture built for it.
A Halbach array is an assembly of separate magnets, each oriented at a rotating angle, so flux is concentrated on one side of the array and largely cancelled on the other. It is a way to arrange discrete parts, used where a strong one-sided field is wanted.
A coded magnet, sold by Correlated Magnetics Research as the Polymagnet, carries a designed and often irregular pattern of many small regions on one piece. The pattern is chosen for a behavior between two mating parts: alignment, latching, a contactless spring, rotational detents. CMR designs the pattern in software and prints it with a programmable magnetizer, so no dedicated fixture is needed per design.
One note for anyone designing around these: CMR states on its FAQ that its patents typically cover behaviors regardless of whether they are achieved with Polymagnets, conventionally magnetized magnets or assemblies of discrete magnets. Check freedom to operate before building a look-alike from separate magnets.
WholeMagnetics, 2026-10-04. Polymagnet facts are taken from Correlated Magnetics Research’s public pages, listed below; vendor performance figures are CMR’s own.