Microstructural and permeability studies on nano-crystaline Ni 0.50-xMnxCu0.50Fe2O4 prepared by combution technique

Abstract

Improved magnetic and micro-structural properties were achieved by doping of Mn component in a series of nanocrystalline spinel type ferrites Ni0.50-xMnxCu0.50Fe2O4, where x=0.00 to 0.40 in steps of 0.10. These are synthesized by combustion technique heat treated at temperatures varying from 1150 to 1300˚C in air for 6 hours. X-ray diffraction data (XRD) used to characterize the crystallization behavior of the samples sintered at 1200˚C. Lattice parameters were calculated using the Nelson Riley function. The lattice constant increases linearly with the increase of Mn content, obeying Vegard’s law. From the XRD pattern of the calcined powders nanosized particles were found in the range from 27 to 48 nm. The density of the compositions measured by Archimedes’s principle at sintering temperature 1150˚C to 1300˚C, it increases with increases of Mn content for x=0.00 to 0.20 then it decreases up to x=0.40. Porosity showed opposite trend of density. From the optical micrographs of various compositions it was found that due to increase of small amount of Mn content the average grain size increases very high and further increases of Mn content grain sizes become smaller, as excess amount of Mn does not favor the further grain growth. Actually grain sizes are increases, by magnifying the grain it was found that bigger grains were broken into smaller grains. At the increase of sintering temperature grain size increases. Observing different sintering temperatures with increasing Mn2+content, the real part of complex permeability increases from 30 to 112, RQF increases from 105 to 2624 and the loss factor decreases from 0.26 to 0.04. It was observed that and RQF increases with increasing sintering temperatures. The real part of complex permeability as a function of temperature for various Ni0.50-xMnxCu0.50Fe2O4 ferrites sintered at 1200˚C were observed that the Néel temperature decreases with the increases of Mn contents from 853 to 693K. From DC magnetization data it is clear that at room temperature all samples are in ferrimagnetic state sintered at 1200˚C. From this data we found the saturation magnetization, Ms increases from 1.15×105A/m to 2.8×105A/m with increasing Mn contents from x=0.00 to 0.30. But it decreases with further increase of Mn for x>0.30 and found 2.31×105A/m, which is the possibility of non-collinear spin canting effect. By the micro-structural and permeability studies we observed samples for x=0.00 and 0.10 have less density, high porosity, porous microstructure, low initial permeability, low quality factor and high loss factor. On the other hand for the sample x=0.40 initial permeability and relative quality factor have the highest value and loss factor has the lowest value at sintering temperature 1300˚C.