Is ball milling a worthy route to produce magnetic semiconductors?

We present a study of the magnetic and structural effects generated by ball milling on different compounds recently reported as room-temperature magnetic semiconductors: a stoichiometric mixture of ZnO and MnO2 and single-phase samples of Zn0.96M0.04O (MCo and Mn). In general, a dramatic reduction of the average crystal size is observed. None of our samples present a ferromagnetic state induced by ball milling, in contradiction with previous results.