Dependence of Magnetic Properties of ZnO:Mn Nanocrystals on Synthesis Conditions

Authors О.V. Kovalenko , V.Yu. Vorovsky

O. H. Dnipro National University, 72, Gagarin St, 49010 Dnipro, Ukraine

Issue Volume 14, Year 2022, Number 3
Dates Received 24 September 2021; revised manuscript received 26 June 2022; published online 30 June 2022
Citation О.V. Kovalenko, V.Yu. Vorovsky, J. Nano- Electron. Phys. 14 No 3, 03030 (2022)
PACS Number(s) 75.75. + a, 81.07. – b, 85.35.p
Keywords Zinc oxide (10) , Nanocrystals (3) , Ultrasonic spray pyrolysis, Cryochemical synthesis, Defects (12) .

The results of studies of samples of ZnO:Mn nanocrystals with a Mn concentration of 2 at. % obtained by ultrasonic spray pyrolysis and cryochemical synthesis methods are presented. The precursors were zinc and manganese nitrates and acetates, respectively. Samples were studied by XRD, EPR and vibrational sample magnetometry. It was found by XRD that the crystal lattice parameters of nanocrystals in the samples are much lower than those of single-crystal ZnO. This indicates the presence of defects and deformation stresses in nanocrystals. The EPR method shows that in the samples obtained by ultrasonic spray pyrolysis, defects and Mn2+ impurity ions are located not in the bulk, but in the surface layer of nanocrystals. Samples obtained by cryochemical synthesis method have a large number of acceptor-type defects. The magnetization of these samples is significantly higher than that of the samples obtained by ultrasonic aerosol pyrolysis. This may be due to the fact that in the samples obtained by ultrasonic spray pyrolysis ferromagnetism occurs on the surface, and in the samples obtained by cryochemical synthesis – in the bulk of nanocrystals. It is caused by the destructive action of special gaseous medium, which is formed during the thermal decomposition of zinc acetate. Such conditions of cryochemical synthesis methods lead to the appearance of a large number of bulk defects in nanocrystals.

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