Localized ferromagnetic charge ordering through charge density analysis in nano sized diluted magnetic semiconductor Co²⁺:ZnO

Nano sized diluted magnetic semiconductor Co²⁺:ZnO (with composition Zn_0.99Co_0.01O) was prepared by sol-gel method and studied for the effect of annealing on ferromagnetic charge ordering using charge density studies. Powder XRD data sets of the samples annealed at various temperatures (500, 600, 700, 800 and 900 °C) have been investigated by the Rietveld refinement analysis and the charge density distribution using the maximum entropy method (MEM). The mid bond electron densities between the Zn(Co) and O atoms are analyzed to understand the origin of ferromagnetic behaviour between the temperature range 600-700 °C. Zn_0.99Co_0.01O is found to switch "on" the ferromagnetic behaviour range 600-700 °C and then to switch "off". The charge ordering that results in ferromagnetic occurrence is dealt for the first time through charge density route.