Using nanolithographic techniques we deposit an array of ferromagnetic dysprosium dots with perioda=500 nm on top of GaAs–AlGaAs heterojunctions. The spatially periodic stray fields affect drastically the magnetotransport properties of the electrons in the underlying two‐dimensional electron gas and give rise to the long predictedmagneticcommensurability oscillations. We show that such a semiconductor‐ferromagnet hybrid system can be used to study the magnetic properties of nanoscale particles. ©1995 American Institute of Physics.