RESEARCH PAPER Doping effects on the structural, magnetic, and hyperfine properties of Gd-doped SnO 2 nanoparticles H. Coelho-Ju ´ nior • J. C. R. Aquino • F. H. Arago ´n • P. Hidalgo • R. Cohen • L. C. C. M. Nagamine • J. A. H. Coaquira • S. W. da Silva • H. F. Brito Received: 28 May 2014 / Accepted: 1 October 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract In this work we present the study of the structural, magnetic, and hyperfine properties of Gd- doped SnO 2 nanoparticles synthesized by a polymer precursor method. The X-ray diffraction data analysis shows the formation of the rutile-type structure in all samples with Gd content from 1.0 to 10.0 mol%. The mean crystallite size is *11 nm for the 1.0 mol% Gd- doped samples and it shows a decreasing tendency as the Gd content is increased. The analysis of magnetic measurements indicates the coexistence of ferromag- netic and paramagnetic phases for the 1.0 mol% Gd- doped sample; however, above that content, only a paramagnetic phase is observed. The ferromagnetic phase observed in the 1.0 mol% Gd-doped sample has been assigned to the presence of bound magnetic polarons which overlap to create a spin-split impurity band. Room-temperature 119 Sn Mo ¨ssbauer measure- ments reveal the occurrence of strong electric quad- rupole interactions. It has been determined that the absence of magnetic interactions even for 1.0 mol% Gd-doped sample has been related to the weak magnetic field associated to the exchange interaction between magnetic ions and the donor impurity band. The broad distribution of electric quadrupole interac- tions are attributed to the several non-equivalent surroundings of Sn 4? ions provoked by the entrance of Gd 3? ions and to the likely presence of Sn 2? ions. The isomer shift seems to be nearly independent of the Gd content for samples with Gd content below 7.5 mol%. Keywords Gd-doped SnO 2 nanoparticles  Magnetic properties  Structural properties  Mo ¨ssbauer spectroscopy  Spintronics Introduction Oxide semiconductors are interesting matrices for producing the so-called oxide-diluted magnetic semi- conductor (ODMS) systems. These materials have drawn considerable attention due to their potential in H. Coelho-Ju ´nior  J. C. R. Aquino  F. H. Arago ´n  J. A. H. Coaquira (&)  S. W. da Silva Nu ´cleo de Fı ´sica Aplicada, Instituto de Fı ´sica, Universidade de Brası ´lia, Brası ´lia, DF 70910-900, Brazil e-mail: coaquira@unb.br F. H. Arago ´n  J. A. H. Coaquira  S. W. da Silva Instituto de Cie ˆncias Biolo ´gicas, Po ´s-graduac ¸a ˜o em Nanocie ˆncia e Nanobiotecnologia, Universidade de Brası ´lia, Brası ´lia, DF 70910-900, Brazil P. Hidalgo Faculdade Gama-FGA, Setor Central Gama, Universidade de Brası ´lia, Brası ´lia, DF 72405-610, Brazil R. Cohen  L. C. C. M. Nagamine Instituto de Fı ´sica, Universidade de Sa ˜o Paulo, Sa ˜o Paulo, SP 05508-090, Brazil H. F. Brito Instituto de Quı ´mica, Universidade de Sa ˜o Paulo, Sa ˜o Paulo, SP 05508-000, Brazil 123 J Nanopart Res (2014) 16:2689 DOI 10.1007/s11051-014-2689-3