Structural and magnetic characteristics of Co_{1鈭?span style='font-style: italic'>x}Ni_x/2Sr_x/2Fe₂O₄ nanoparticles

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• 作者：Ali Ghasemi^a ; ^{ali13912001@yahoo.com} ; Andrea Paesano Jr.^b ; Carla Fabiana Cerqueira Machado^b
• 关键词：Ferrite ; Magnetic property
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2012
• 期刊代码：31_03048853
• 类别：ph
• 出版时间：July, 2012
• 卷：324
• 期：14
• 页码：2193-2198
• 文件大小：1412 K

摘要

Co_1鈭?em>xNi_x/2Sr_x/2Fe₂O₄ (x=0-0.5 in steps of 0.1) ferrite nanoparticles have been synthesized at room temperature, without calcination, using a reverse micelle process. The site preference was determined by M枚ssbauer spectroscopy at 300 K. The hyperfine parameters were obtained, for the whole series of solid solutions. For the X鈮?.20 samples, the spectra were fitted with two discrete sextets and for the X>0.20 samples, a magnetic hyperfine field distribution and a doublet were also imposed in the fit procedure. Hysteresis loops were measured using a superconducting quantum interference device magnetometer at 2 K and 300 K. The results indicate that the relative decrease in saturation magnetization of nanoparticles compared to the submicron particles could be attributed to a surface spin termination and disorder. Magnetic dynamics of the nanoparticles was studied by the measurement of ac magnetic susceptibility versus temperature at different frequencies and it is found that the results are well described by the Vogel-Fulcher model.