Application note:
Bucking magnets mounted on the back of the motor system are used to achieve semi magnetic shielding and/or higher magnetic flux density in the air gap. The bucking magnet must repel the motor system - this is important. However, when it comes close to the back plate of the motor system it will catch, so mind your fingers. Use a 2-component adhesive intended for ceramics and metal. Drops of super glue may be used to fix the magnet while the adhesive hardens.
Attention: Mind your fingers when handling magnets!