Nanoparticles of pure and substituted maghemites (γ-M xFe 2-xO 3 where M = Al, Cr, Mn, Zn and 0 ≤ × ≤ 1.3): A comparative study

Abstract

Magnetic nanoparticles of pure and substituted iron oxides are prepared by single step autocombustion or by wet chemical methods. The nanoparticles prepared by the first process had mixed phase of hematite and maghemite whereas the later essentially gives maghemite phase. XRD patterns and TEM micrographs of the pure and substituted maghemites samples suggest about their monopha-sic nature and inverse spinel structure. Further, the size of the particles for the above iron oxide samples was found to be in the range of 4 to 30 nm. Saturation magnetization value for the samples was observed to be varying with the type and the amount of substitution. For example, magnetization value initially increased and then decreased for Al- and Mn-substitutions but it continuously decreased for Cr- and Zn-substitutions. Contrary to the saturation magnetization value, the Curie temperature decreased continuously with increased substitutions irrespective of the type of substitutions. Due to higher magnetization value of Mn-substituted maghemite (for x = 0.2, 78 Am 2/kg), it has higher heating ability and specific absorption rate compared to Al-substituted maghemite (for x = 0.07, 70 Am 2/kg) and pure maghemite (62 Am 2/kg). © 2011 American Scientific Publishers.