Síntese, caracterização e estudo das propriedades magnéticas, ópticas e elétricas de nanopartículas de ZnO:Co
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Data
2014-05-13
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Universidade Federal de Goiás
Resumo
This work has as a general proposition the production of a DMS based on ZnO
semiconductor and Co transition metal, as well as the study of the origin of ferromagnetism in
these materials using the models of magnetic interaction in the literature. The combustion
reaction was chosen as a synthesis route for the production of samples Zn1 - x Co x O with molar concentrations of x= 0,00, 0,005, 0,01, 0,03, 0,05, 0,07 and 0,09. The samples were obtained in the form of powders and chemical, structural and morphological characterization performed by EDS, DRX e MET measures. These characterizations indicated good crystallinity with the formation of the hexagonal crystalline phase wurtizita characteristic of ZnO without adding spurious phase for all molar concentrations. Powders presented nanometric dimension (~ 18 nm) with spherical particle shape and molars contractions of very similar elements of stoichiometric proposals. The optical characterizations via FTIR e UV-Vis confirmed the presence of the bond Zn - O and the replacement of Zn for Co in tetrahedral sites in ZnO crystal structure in the samples with x 0,00. By UV-Vis spectroscopy was also
possible to obtain the optical bandgap values of the samples and confirm the semiconducting
property, as well as calculate the dielectric constant of these materials. Magnetic
characterizations performed by VSM measures (room temperature and high temperature) and
Magnetometry at low temperatures indicated wide variety of magnetic systems in the studied
temperature range. The x = 0,05 sample showed ferromagnetism across the temperature range of 5< Y (K) < 594. This same sample showed a value of 2,66 effective moment magnetic
dipole and 2,52 for the saturation magnetization at low temperatures, that are
significant results compared to several papers published. Through adjustments to the
theoretical models, the ferromagnetism at low temperatures was attributed to the BMP
magnetic interaction model. The room temperature ferromagnetismo was attibuted to the
RKKY interaction model due to the high density of defects and free charge carriers in the
samples.
Descrição
Palavras-chave
DMS , ZnO , Ferromagnetism , Reação de combustão , BMP , Spintrônica , Combustion reaction , Spintonics
Citação
PESSONI, H. V. S. Síntese, caracterização e estudo das propriedades magnéticas, ópticas e elétricas de nanopartículas de ZnO:Co. 2014. 120 f. Dissertação (Mestrado em Física) - Universidade Federal de Goiás, Goiânia, 2014.