Structural and magnetic properties of ZnO and Zn 1x Mn x O nanocrystals N.O. Dantas a , L. Damigo a , Fanyao Qu a , R.S. Silva a,b, * , P.P.C. Sartoratto c , K.L. Miranda c , E.C. Vilela c , F. Pelegrini d , P.C. Morais b a Universidade Federal de Uberlândia, Instituto de Física, Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Uberlândia MG 38400-902, Brazil b Universidade de Brasília, Instituto de Física, Núcleo de Física Aplicada, Brasília DF 70910-900, Brazil c Universidade Federal de Goiás, Instituto de Química, Goiânia GO 74001-970, Brazil d Universidade Federal de Goiás, Instituto de Física, Goiânia GO 74001-970, Brazil article info Article history: Available online 25 August 2008 PACS: 75.75.+a 76.30.v 77.84.Lf 78.67.Bf 78.70.Ck Keywords: Biomaterials Nanocrystals X-ray diffraction Nano-composites abstract Chemical precipitation of metal-ions from aqueous solution has been successfully used to produce Zn 1x Mn x O nanocrystals, in the form of nano-powder. X-ray diffraction (XRD) measurements reveal that the as-prepared samples are single-phase materials and their lattice constant changes with the variation of Mn-concentration, which indicates the incorporation of Mn 2+ into the hosting ZnO. These findings are corroborated by the observation of the well defined six hyperfine lines of Mn 2+ ion in the electron para- magnetic resonance (EPR) spectra of the samples with a low Mn-concentration, and of a broad EPR line, which manifests the onset of Mn–Mn exchange interaction, in the samples with an elevated value of x. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction The recent development of diluted magnetic semiconductor (DMS) materials down to the nanoscale dimension, partially in re- sponse to demands coming from spintronics for new and improved materials, has extensively spread throughout several fields of sci- ence and technology [1–3]. DMS are semiconductors to which a magnetic impurity is intentionally introduced – a small fraction of the native atoms in the hosting non-magnetic semiconductor mate- rial is replaced by magnetic atoms. The main characteristic of this new class of compounds is the possibility of the onset of an ex- change interaction between the hosting electronic subsystem and electrons originating in the partially-filled d or f levels of the intro- duced magnetic atom [4–6], which enables a control of both the optical and magnetic properties of the end material using external fields in regimes hardly achieved with other classes of materials. Among semiconductor materials, the wide band-gap (3.37 eV) ZnO has attracted a particular attention due to its special interesting physical properties [7]. In this study, we report on the synthesis of Zn 1x Mn x O(x P 0) nanocrystals (NCs) using the chemical precipita- tion of metal-ions in aqueous solutions. The structural and magnetic properties of these NCs, observed by X-ray diffraction (XRD) and X-band electron paramagnetic resonance (EPR), are also presented. 2. Experimental details The preparation of the Zn 1x Mn x O(x P 0) NC samples is based on the chemical transformation of the [Zn(NH 3 ) 4 ] 2+ complex in the presence of sodium oleate, hydrazine sulfate, and manganese chlo- rite at 80 °C. The pH value of the reaction medium is maintained at 8.5 during the entire chemical process, using sodium hydroxide aqueous solution. Shortly, 100 mL of 0.38 mol/L zinc chlorite and 1.6 mol/L ammonium hydroxide aqueous solutions are mixed to- gether and stirred for 30 min to produce the [Zn(NH 3 ) 4 ] 2+ complex in solution. Then, 1.0 mL of hydrazine sulfate and 0.08 g of sodium oleate are added into the reaction medium. The obtained final solu- tion was maintained at 80 °C in water-bath to transform the [Zn(NH 3 ) 4 ] 2+ complex while the pH value of the reaction medium is maintained at 8.5 using 4 mol/L sodium hydroxide aqueous solu- tion. The reaction is carried out for 2 h, and the resulting white precipitates are percolated and washed with distilled water and absolute ethanol for several times. After that they are dried up at 60 °C by 12 h and successively at 500 °C by 2 h. 0022-3093/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2008.04.024 * Corresponding author. Address: Universidade de Brasília, Instituto de Física, Núcleo de Física Aplicada, Brasília DF 70910-900, Brazil. Tel.: +55 34 32394281; fax: +55 34 32394106. E-mail addresses: noelio@ufu.br (N.O. Dantas), ricssilva@yahoo.com.br (R.S. Silva). Journal of Non-Crystalline Solids 354 (2008) 4727–4729 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol