جستجوی مقالات مرتبط با کلیدواژه « ferromagnetism » در نشریات گروه « مواد و متالورژی »

The work is the report about stearic acid sol-gel synthesis method, magnetically, electricalcharacterization and activation energy of copper manganese oxide nanostructures. The CuMn2O4 nanostructures are synthesized at a temperature of 600°C using the sol-gel method. The structural analysis using X-ray diffraction (XRD) and Scherrer equation show that the crystallite size of CuMn2O4 is about 23.0 nm. The activation energy value is measured by temperature-programmed reduction (TPR) analysis at three heating rates of 10, 15 and 20 °C/min and Kissinger equation .The Ea value is 28.1 kJ/mol. Vibrating sample magnetometer (VSM) analysis of the nanostructures indicates moderateferromagnetic properties. Examination of the dielectric properties by the LCR meter indicates the semiconducting property of the nanostructure. The highest conductivity increase was in the frequency of 308 MHz equal to 70.7 μS. Therefore, the CuMn2O4 nanostructures are potential candidates in fuel cells, telephones, loudspeakers and transformers due to their properties and convenience, non-toxic and environmentally friendly production methods.

In this work we report synthesis and magnetic characterization of cobalt doped ZnO nanoparticles (with different percent of doped cobalt oxide). Synthesis of the materials was carried out at room temperature by polyacrylamide-gel method, using zink sulfate and cobalt nitrate as source materials, acrylamide as monomer and N,N-methylene bisacrylamide as a lattice reagent. Characterization of the samples were performed using XRD, SEM, TEM, UV and photoluminescence (PL) studies. The X-ray diffraction patterns obtained showed formation of wurtzite ZnO structure with no secondary Co phases. The EDS measurements were employed to investigate the composition of the samples and showed the presence of Zn and cobalt elements detected.The optical absorption spectra showed internal d-d transitions related to Co2+ incorporated on the Zn lattice site of ZnO structure. The red-shift of the band-gap edge has been attributed to a merging of donor and conduction bands due to the Co doping. The magnetic behavior of prepared cobalt doped samples was finally investigated at room temperature using vibrating sample magnetometer (VSM). The results show that, the Co doped ZnO. Nanoparticles with 2at% CoO is ferromacnetic at RT. This magnetic property is greatly suppressed and replaced by a paramagnetism behavior at higher doping levels.