The Halbach Array is a special arrangement of permanent magnets that augments the magnetic field on one side of the array, while reducing the field to near zero magnetic field on the other side. This is achieved by having a spatially rotating of magnetization. The Halback array will generate a high and uniform magnetic field within a certain area, and its magnetic field strength will exceed the residual magnetism of the magnetic material itself.  It can be achieved much stronger magnetic field with fewer magnets. 

Application:

Linear Halbach Arrays:

Such as brushless AC motors, voice controlled coils, magnetic drug targeting to high-tech applications, such as swing magnets for particle accelerators and free electron lasers.

Cylinder Halbach Arrays:

Such as brushless AC motor, magnetic couplings and high magnetic field cylinders