5987

5595

كارشناسي ارشد

ماده چگال

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1389

[نه]،85ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

پرويز كاملي

هادي سلامتي

10/3/90

جواد هاشمي فر، مهدي رنجبر

فيزيك

ID5595

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Preparation and investigation of magnetic electrical and structural properties of LaMn1 xCuxO3 0 00 x 0 125 manganite Student name Hajar Sadat Vaezi Email address h vaezi@ph iut ac ir Date of submission 1389 11 16 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Parviz Kameli kameli@cc iut ac ir Abstract In this thesis the effect of Cu substitution and synthesis condition on the structural magnetic and electrical properties of LaMn1 xCuxO3 0 00 x 0 125 manganite have been investigated Samples have been prepared by new solid state method In order to investigate the influence of sintering temperature on various properties of the compounds the sample x 0 05 divided into two series and sintered at 1200 and 1350 centigrade degree The samples were sintered in 12000C named T1 and 13500C named T2 The analysis of the XRD pattern showed that all samples except x 0 075 have orthorhombic structure with pnma space group and sample x 0 075 has rhombohedral structure with R3C space group The structural parameters and space groups have been obtained by FullProf software Rietveld refinement Rietveld analysis s comparison of T1 and T2 samples showed that sintering temperature has no considerable effect on the samples structure The AC magnetic susceptibility measurements showed that the curie temperature increased with increasing the Cu content until x 0 075 and then decreased in x 0 125 This means that the double exchange interaction becomes weak with high Cu doping and increases in low Cu doping All doped samples in low temperature showed a drop in the real part and a peak in imaginary part of AC magnetic susceptibility curves The peak is related to spin glass state in the samples The AC susceptibility depends on the frequency and field Fitting with conventional critical slowing down model demonstrates that samples are the spin glass at low temperatures According to the electrical resistivity measurements the increasing of the substitution content till x 0 075 results in decreasing of electrical resistivity and increasing of electrical resistivity at higher level of doping Fitting of electrical resistivity plots with small polaron hoping SPH and variable range hoping VRH models demonstrates the nice agreement by the SPH model Fitting of electrical resistivity of all samples showed that with increasing the Cu doping polaron activation energy decreases and in x 0 125 it starts to increase Kay words manganite spin glass AC susceptibility sintering doping Super exchange double exchange

پرويز كاملي

هادي سلامتي

جواد هاشمي فر، مهدي رنجبر