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ZnO is an attractive system for a wide variety of practical applications, being a chemically stable oxide semiconductor. It has been shown that Fe doping produces ferromagnetic semiconductor at room temperature. This material, therefore, has the potential for use in spintronic devices such as spin transistors, spin light emitting diodes, very high density nonvolatile semiconductor memory and optical emitters. It is believed that oxygen vacancies and substitutional incorporation are important to produce ferromagnetism in semiconductor oxide doped with transition metal ions. The present paper reports detailed electron paramagnetic resonance investigations (EPR) of the samples in order to investigate how annealing atmosphere (Air and Argon) influenced the magnetic behavior of the samples. X-band electron paramagnetic resonance (EPR) studies of Fe3+ ions in Zn1-xFexO powders with x = 1%, 3% is reported. These samples are interesting to investigate as Fe doping produce ferromagnetism in ZnO, making a promising ferromagnetic semiconductor at room temperature. [ABSTRACT FROM AUTHOR]

Mn-doped ZnO particles (x = 0.01 and 0.03) have been successfully prepared and sintered at 600 °C in air and argon atmosphere, respectively. The effects of annealing atmosphere on the structural, morphological and magnetic properties of obtained samples were studied. XRD studies reveal a wurzite-type structure for the samples with x = 0.01, while the formation of the secondary phases were evidenced for x = 0.03 samples. The samples annealed in Ar have much better crystallization. All EPR spectra present a hyperfine structure specific to isolated Mn2+ ions and for the sample x = 0.03 annealed in air, a new resonance line arises, which could be attributed to a ferromagnetic phase. [ABSTRACT FROM AUTHOR]

This paper reports the influence of the annealing in air and argon atmosphere on the structural and magnetic characteristics of Co-doped ZnO powders. XRD studies reveal a wurzite- type structure, while the formation of Co3O4 secondary phase was evidenced by Raman spectroscopy only for the sample annealed in air. A ferromagnetic behavior was observed for the sample annealed in air atmosphere and this behavior was explained. The sample annealed in argon atmosphere presents a paramagnetic behavior. [ABSTRACT FROM AUTHOR]