An X-band Co2+ EPR study of Zn1−xCoxO (x=0.005–0.1) nanoparticles prepared by chemical hydrolysis methods using diethylene glycol and denaturated alcohol at 5 K

• 5 K X band Co2+ EPR investigations on QC and NC ZnO dilute magnetic semiconductor nanoparticles.
• NC and QC samples exhibited high-spin Co2+ EPR lines and ferromagnetic resonance line.
• NC sample also exhibit line due surface oxygen vacancies.
• FMR line is more intense in QC than that in NC samples.
• Magnetic states and the origin of ferromagnetism are discussed.

EPR investigations on two types of dilute magnetic semiconductor (DMS) ZnO nanoparticles doped with 0.5–10% Co2+ ions, prepared by two chemical hydrolysis methods, using: (i) diethylene glycol ((CH2CH2OH)2O) (NC-rod-like samples), and (ii) denatured ethanol (CH3CH2OH) solutions (QC-spherical samples), were carried out at X-band (9.5 GHz) at 5 K. The analysis of EPR data for NC samples revealed the presence of several types of EPR lines: (i) two types, intense and weak, of high-spin Co2+ ions in the samples with Co concentration >0.5%; (ii) surface oxygen vacancies, and (iii) a ferromagnetic resonance (FMR) line. QC samples exhibit an intense FMR line and an EPR line due to high-spin Co2+ ions. FMR line is more intense, than the corresponding line exhibited by NC samples. These EPR spectra varied for sample with different doping concentrations. The magnetic states of these samples as revealed by EPR spectra, as well as the origin of ferromagnetism DMS samples are discussed.