We report on the magnetic and transport measurements in an Fe-doped colossal magnetoresistance compound (La 0.65 Ca 0.35 MnO 3 ). Increased spin disorder and a decrease of T c with increasing Fe content are evident. We find that the resistivity data above T p fits better to a variable range hopping model and the localization length decreases with Fe content. The variations in the critical temperature T c , confinement length, magnetic moment and magnetoresistance show a rapid change at about 4-5% Fe. The maximum magnetoresistance is seen to increase consistently with the addition of Fe and increases up to 400% for 8% Fe. 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.

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This paper addresses the effect of Mn (2%, fixed) and Co (2, 4, and 6%, varied) substitution on the structural, optical, dielectric and magnetic responses of ZnO nanoparticles synthesized by the co-precipitation chemical route.