Local electronic structure of Mn dopants in ZnO probed by resonant inelastic x-ray scattering

The electronic structure of Mn dopants in ZnO epitaxial thin films synthesized at different temperatures has been investigated using resonant inelastic x-ray scattering. The resulting Mn L2,3 x-ray emission spectra of Zn0.8Mn0.2O (resonantly excited at L2 and L3 absorption edges) reveal different spectral features depending on the growth temperature of the films. The relative integral intensity ratio of Mn L2 to Mn L3 emission lines is greatly suppressed in the case of nonmagnetic Zn0.8Mn0.2O grown at 700 deg C due to L2L3M4,5 Coster-Kronig transitions. The ferromagnetic sample grown at 600 deg C exhibits a normal oxide structure. The results suggest that a high growth temperature causes direct Mn-Mn bonds from the segregation of Mn atoms in ZnO. Therefore the disappearance of ferromagnetism in Mn-doped ZnO can be attributed to antiferromagnetic Mn-Mn exchange interactions due to the inhomogeneous local environment around the Mn impurities.