What is the purpose of perpendicular "smaller" magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?
This is more or less just transferred from Wikipedia, however:

As @HarrySvensson indicates, this is a Halbach array, apparently used to create a magnetic field that is stronger on one side than the other.  Images from wikipedia:



So you can see that when they are arranged this way, the magnets create strong wide poles on one side and alternating narrow poles on the other side to cancel each other out.  The field generated looks like this:(Also from wikipedia)

Used in a generator, this creates a stronger field on the inside for power generation and a weaker field on the outside to minimize the mass of silicon steel needed to confine the magnetic path.

Edit: Having tried to configure magnets into this arrangement I will note that strong rare earth magnets strongly disagree with being placed together this way! a strong mechanical setting and retention mechanism is necessary in order to use this type of array!