مطالعه آثر آلايش Zn، اثر دماي باز پخت و پوشش PVA بر ويژگي هاي ساختاري و مغناطيسي نانو ذرات ﴿Ni1-xZnXFe2O4﴾

چكيده انگليسي :

The effect of zinc doping temperature annealing and polyvinyl alcohol PVA coating on structural and magnetic properties of Ni1 xZnxFe2O4 ferrite nanoparticles Mozhdeh Rahimi m rahimichermahini@ph iut ac ir Date of Submission 2013 16 01 Department of physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Dr Parviz Kameli kameli@cc iut ac ir Dr Mehdi Ranjbar ranjbar@cc iut ac ir Abstract The spinel ferrite nanoparticles due to characteristics such as high permeability and low coercivity have been widely used in industry and medicine But a simple reproducible and low cost fabrication method by which magnetic nanoparticles are synthesized with high homogeneity and purity has always been a concern of researchers Therefore in this study nanocrystalline NixZn1 xFe2O4 ferrites the most commonly used magnetic materials among the spinel ferrites have been synthesized via sol gel auto combustion method using EDTA as a complexion agent that prevents oxidation and interaction of metal cations with the surrounding ions and causes the formation of finer particles This study consists of three parts In the first part we have investigated the effect of Zn substitution on structure and magnetic properties of nickel ferrite and in the second part the effect of sintering temperature and then in the third part the effect of polyvinyl alcohol PVA coating on structural magnetic properties and spin dynamics of Ni 0 3Zn0 7Fe2O4 ferrite nanoparticles have been studied using analysis such as X ray diffraction XRD Furier Transform Infrared FTIR microscopic imaging FE SEM and TEM vibrating sample magnetometer VSM and ac susceptibility measurements The XRD patterns indicated that the crystalline structure is single phase cubic spinel for all samples and the MAUD results indicate that the synthesized nickel ferrite NiFe2O4 and the zinc ferrite ZnFe2O4 nanocrystals have inverse and normal spinel structure respectively Ni1 xZnxFe2O4 ferrites 0 x 1 have a mixed spinel structure The VSM data showed that by increasing Zn doping level up to x 0 3 the magnetization was increased and it was decreased by further increase in x due to the weakening of the superexchange interaction at the octahedral sites The magnetocrystalline anisotropy constant of Ni ferrite is larger than that of Zn ferrite Therefore the magnetocrystalline anisotropy constant decreases with the replacement of Zn2 ion by Ni2 ion which implies an decrease in Hc The XRD patterns of the samples annealed at different temperatures 350 1200 C showed the peaks width reduces by increasing sintering temperature indicating the crystallite size enhancement during sintering process at elevated temperatures Saturation magnetization Ms increases with increasing sintering temperature and can be caused due to three reasons 1 In the larger nanoparticles high crystallinity and a low amount of microstructure defects allow domain walls to move easily in the magnetization process 2 In the Core shell morphology the higher core shell ratio of large particles leads to eliminations of surface effects and consequently enhancement of Ms and 3 by increasing the sintering temperature the extra Fe3 ions in the A sites start distributing into the B sites and hence the number of Fe3 ions at A site is reduced Consequently the nB increases with increasing sintering temperature due to a decrease in fraction of magnetic moment of A site and an increase in the net magnetic moment of B sites Of course the third reason was confirmed by fitting of XRD patterns using the MAUD software XRD patterns of two samples with and without PVA annealed at 375 C indicated that the crystalline structure is single phase cubic spinel and in which the spinel structure is retained after PVA coating and the increase in Ms after PVA coating could be attributed partly to the nanoparticle s crystal growth after polymer coating The analysis of ac susceptibility curves with critical slowing down model showed th

رحيمي، مژده

مطالعه آثر آلايش Zn، اثر دماي باز پخت و پوشش PVA بر ويژگي هاي ساختاري و مغناطيسي نانو ذرات ﴿Ni1-xZnXFe2O4﴾

فريت هاي اسپنلي , سل-ژل , EDTA , اثر جانشاني Zn , باز توزيع كاتيون ها , مدل مغزه-پوسته , اندازه ي بحراني