Araújo, José Humberto deSilva, Rafael Leal da2019-12-022019-12-022018-11-29SILVA, Rafael Leal da. Síntese e caracterização de nanoestruturas de ferritas dopadas com samário e recobertas com polímeros. 2018. 106f. Tese (Doutorado em Física) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2018.https://repositorio.ufrn.br/jspui/handle/123456789/28101In this work we present the synthesis and characterization of nanoparticles of magnetite and cobalt ferrite doped with Sm: F e2.68Sm0.32O4 and CoF e2−xSmxO4 (x = 0, 0.05, 0.10, 0.15 and 0.20). Magnetite nanoparticles were produced using the polyol method, where the polyvinylpyrrolidone polymer (PVP) was used to protect the nanoparticles from oxidation. The nanoparticles of Sm-doped cobalt ferrites were produced by the ion-coordinated reaction (ICR) method and covered by a chitosan matrix. The crystalline structure and magnetic properties were studied by X-ray di raction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy and DC magnetometry. The magnetite sample has a narrow particle size distribution with a diameter of 5.2 nm. The particles exhibit superparamagnetic behavior at room temperature with mean blocking temperature of TB = 9.9 and magnetocrystalline constant of 4 × 105 J/m3 in 5 K. At room temperature, the M-H curve shows symmetrical behavior (Hc = 0) and the Mössbauer spectrum has a single paramagnetic component, while at 5 K the saturation magnetization is 18.9 emu/g and the M-H curve, eld cooling (FC) exhibits a shift with an exchange bias eld of ∼ 110 Oe The magnetic results are discussed in terms of the cation distribution in the inverse spinel network, as determined by Mössbauer spectroscopy. A small magnetic contribution of the surface layer of nanoparticles was considered in the interpretation of magnetocrystalline anisotropy. The cobalt ferrite samples have particles coated by the chitosan biopolymer with a narrow range of sizes depending on the concentration of Sm ions in the samples ranging from 9.49 nm to 5.62 nm. The values of coercive eld, saturation magnetization and e ective anisotropy underwent sensitive variations with doping. A theoretical adjustment was made taking into account a distribution composed of two types of particles, blocked and superparamagnetic. The Mösssbauer spectrum was only perfectly adjusted when three sextets were used at each crystallographic site at room temperature and 12 K. The Mössbauer results were interpreted considering a random distribution of Sm ions at sites A and B. The release studies were obtained by applying an AC magnetic eld of 70.5 kHz and intensity of 200 Oe. The maximum value obtained from SAR for this sample series was 12.09 W/g, indicating that these particles have potential for use in hyperthermia.Acesso AbertoFerritas dopadasNanopartículasTerra raraPropriedades magnéticasdoctoralThesisCNPQ::CIENCIAS EXATAS E DA TERRA::FISICA