Novel magnetic behavior of Mn-doped ZnO hierarchical hollow spheres

In this study, unique three-dimensional Zn0.98Mn0.02O hierarchical hollow microspheres (HHMs) with diameters of 5-8 mu m have been synthesized by a simple hydrothermal approach. In particular, room-temperature magnetization measurements indicate that novel co-existence of ferromagnetism (FM)/paramagnetism (PM) and only PM behaviors for the as-annealed Zn0.98Mn0.02O HHMs at 673 and 1,073 K, respectively, in Ar gas atmosphere appear, whereas the as-synthesized ones show merely pure FM. Based on the Photoluminescence and Raman spectra, it is confirmed that the concentrations of oxygen vacancies in Zn0.98Mn0.02O HHMs were becoming larger and larger with increasing annealing temperature. Corresponding magnetic evolution mechanism is proposed to relate to oxygen vacancies based on annealing processes. This novel magnetic property will enrich our understanding of diluted magnetic semiconductors.