Exciton quenching and ferromagnetism-to-ferrimagnetism crossover in diluted magnetic semiconducting Zn1-xCoxO nanogranular nanofibers

The synthesis of Co-doped zinc oxide (Zn1-xCoxO) (x = 0, 1.8, 4.4, and 7.2 at.%) nanogranular nanofibers with a diameter of 70- 250 nm and length up to several hundred micrometers by electrospinning and subsequent calcinations is reported. Novel nanoscale Co2+ doping-induced phenomena were found in as-calcined electrospun Zn1-xCoxO nanofibers including (i) thermal decomposition temperature of polyvinyl alcohol (PVA) in PVA/Zn1-xCoxO electrospun composite fibers which is quite different from that of pure PVA electrospun fibers and shows a linear dependence of dopant level, (ii) exciton quenching, (iii) dimensionality-related magnetization and (iv) a room-temperature weak ferromagnetism-to-ferrimagnetism crossover. Finally, an F-centered mechanism is proposed to explain the correlating exciton quenching and the occurrence of ferrimagnetism.