A Halbach Array consists of a special arrangement of permanent magnets deployed to create very strong multipole field on one side of the array and very low leakage fields on the other. Because of this, the magnetic assembly typically doesn’t require a steel backing.
Planar Halbach Arrays limit the field to one side of the plane. Circular Halbach Arrays contain the magnetic field within the ID or outside the OD, depending on the design.
Applications range from holding devices, motor rotors, and magnetic couplings, to various high-energy physics devices.