VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Thursday 8
Dots and wires

› 14:40 - 15:00 (20min)
Competing Interactions in Doped Rare-earth Manganites Nano-Structural Materials
Wiqar Shah  1@  
1 : Federal Urdu Universit  -  Website
Federal Urdu University, Islamabad, -  Pakistan

The effect of Fe doping in La0.65Ca0.35Mn1-xFexO3 (where ) compound on the Mn site has been studied. Resistivity measurements of the compound from ambient temperature down to 77 K exhibit a peak at temperature Tp, which decreases with increasing Fe content. Substantial rise in resistivity corresponding to the Tp and increase spin disorder are also observed with increasing doping. Variable range hopping (VRH), and polaronic have been used to explain the DC transport mechanism in the insulating region above Tp. The localization length is found to decrease by increasing Fe concentration. The variations in the critical temperature Tp, Tc, confinement length, magnetic moment and magnetoresistance show a rapid change at about 4-5\% Fe. Colossal magnetoresistance has been shifted to lower temperature, and enhanced by Fe doping. The maximum magnetoresistance is seen to increase consistently with the addition of Fe and increases upto 400\% for 8\% Fe concentration. However, conduction and ferromagnetism have consistently suppressed by Fe doping. The effect of Fe is seen to be consistent with the disruption of the Mn-Mn exchange possibly due to the formation of magnetic clusters. The formation of ferromagnetic and antiferromagnetic clusters and the competition between them with the introduction of Fe3+ ions, which do not participate in the double exchange (DE) process, have been suggested to explain the low value of magnetization at higher Fe concentration.


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