Local structures of Mn in dilute magnetic semiconductor ZnMnO

The local structures of Mn atoms in (Zn, Mn)O have been investigated by extended x-ray absorption fine structure (EXAFS). For samples with lower Mn concentrations (<11%), EXAFS results show that the majority of Mn atoms are incorporated at Zn substitutional sites. Ferromagnetic behavior has been observed in those ZnMnO samples. It is the direct evidence to suppose that the ferromagnetism in (Zn, Mn)O is not due to Mn-related secondary phases but is intrinsic. When the Mn concentration is increased to 20% or higher, the EXAFS simulation shows the formation of MnO secondary phases and the films show a change from ferromagnetic (FM) to antiferromagnetic (AFM) state. We suggest that Mn-related secondary phases might be responsible for the transformation from FM to AFM state.