Diluted magnetic semiconductors: Mn/Co-doped ZnO nanorods as case study

Abstract

The structure and the magnetic properties of 3 and 5 mol% (based on the starting concentrations) Co- and Mn-doped ZnO nanorods, synthesized by a straightforward and experimentally simple nonaqueous sol–gel route based on benzyl alcohol as solvent, have been investigated by various characterization techniques, including X-ray diffraction with Rietveld refinement, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, magnetization measurements and electron paramagnetic resonance. The doped as-synthesized ZnO nanocrystals retain the wurtzite structure with a morphology in the form of nanorods grown along the [001] direction, whose dimensional parameters as well as degree of agglomeration depend on the type and level of doping. The Co-doped ZnO powders are ferromagnetic with a Curie temperature exceeding room temperature. Conversely, the Mn-doped samples show antiferromagnetic correlations with a possible transition to an antiferromagnetic ground state below TN = 10 K. The results suggest that the magnetic ground state is extremely sensitive to the type of dopant, which is in agreement with previous studies.