Effect of the Milling Conditions on the Properties of ZnO Doped with Fe

Autor: Ligia E. Zamora, D. Salazar, W. R. Aguirre, Á. Casanova, G. A. Pérez Alcázar
Rok vydání: 2018
Předmět:
Zdroj: Journal of Superconductivity and Novel Magnetism. 31:4021-4028
ISSN: 1557-1947
1557-1939
DOI: 10.1007/s10948-018-4657-0
Popis: (Zn0.9Fe0.1)O powders were produced with different ball to powder weight ratios (BPR) by ball milling of ZnO and Fe elemental powders. The BPR used were 15:1, 20:1, 25:1, and 30:1. The prepared samples were studied by x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Mossbauer spectroscopy (MS). The XRD patterns showed a zinc oxide (ZnO) single phase with wurtzite structure, except for the 15:1 ratio, which exhibits an additionally bcc structure associated to α-Fe. The mean crystallite sizes were found to be around 100 A. The Mossbauer spectra were fitted using two doublets, associated to the incorporation of Fe ions into the ZnO lattice, which correspond to the Fe3+ and Fe2+ oxidation states except for the 15:1 ratio, for which an additional sextet was necessary to obtain a good fit, this sextet was associated to segregated Fe into the sample. The increase of the BPR allowed that all Fe penetrated into the ZnO matrix. The magnetization measurement using VSM reveals that the system exhibits ferromagnetic behavior at room temperature. For sample with BPR 15:1, the ferromagnetism is due to the segregated Fe, and for higher BPRs, from 20:1 up to 30:1, we propose that their ferromagnetism is due to the percolation of polarons. These polarons appear due to the oxygen vacancies (detected by XRD) which are occupied by electrons, which appear in the charge balance. Exchange interaction between the electron spins located in the vacancies or holes and those of the magnetic impurities (Fe atoms) leads to the formation of bound magnetic polarons, which percolate, producing in this way magnetic behavior.
Databáze: OpenAIRE
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