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Absence of ferromagnetic order in high quality bulk Co-doped ZnO samples

2010; American Institute of Physics; Volume: 108; Issue: 3 Linguagem: Inglês

10.1063/1.3459885

1520-8850

H. B. de Carvalho, Marcio Peron Franco de Godoy, R. W. D. Paes, Mohammad Hedayetullah Mir, A. Ortiz de Zevallos, F. Iikawa, M. J. S. P. Brasil, V. A. Chitta, Wilmar Barbosa Ferraz, M. A. Boselli, Antônio Claret Soares Sabioni,

Magnetic and transport properties of perovskites and related materials

Bulk Zn1−xCoxO samples were synthesized via standard solid-state reaction route with different Co molar concentrations up to 21%. A detailed microstructural analysis was carried out to investigate alternative sources of ferromagnetism, such as secondary phases and nanocrystals embedded in the bulk material. Conjugating different techniques we confirmed the Zn replacement by Co ions in the wurtzite ZnO structure, which retains, however, a high crystalline quality. No segregated secondary phases neither Co-rich nanocrystals were detected. Superconducting quantum interference device magnetometry demonstrates a paramagnetic Curie–Weiss behavior with antiferromagnetic interactions. We discuss the observed room temperature paramagnetism of our samples considering the current models for the magnetic properties of diluted magnetic semiconductors.