The stadium magnets were designed to have the south pole facing upwards. Spin gears for the MG system came in three varieties: Neo South, North and MW (metal weight). Neo South cores would repel stadium magnets and allow a beyblade to move around the stadium for attack. Neo North cores attract stadium magnets and can be used for defense. MW cores are non-magnetic, only containing a weight block.
For Takara versions, only a certain selection of beyblades have magnetic cores which would otherwise need to be purchased separately. Hasbro usually added magnetic cores to beyblades which Takara did not release with a magnetic core..