Origin of Ferromagnetism in Al and Ni Co-doped ZnO Based DMS Materials

Zn0.95Ni0.05O and Zn0.90Ni0.05Al0.05O compositions of nanocrystallites are synthesised using the well recognised auto-combustion technique.The x-ray diffraction patterns demonstrate the phase pure characteristic wurtzite-type crystal structure with space group P63mc in both the compositions.The elemental incorporation of Ni and Al contents into the ZnO structure is confirmed by energy dispersive x-ray analysis.The micrographs of scanning electron microscopy show an approximate ordered morphology.The electrical resistivity is observed to decrease with the rising temperature,depicting the characteristic semiconductor behaviour of the samples.The lower values of resistivity and ferromagnetic interactions in the Al-doped sample correspond to an increase of carrier's density.It is observed that the carrier mediated mechanism is mainly responsible for ferromagnetism in ZnO-based diluted magnetic semiconductors.