Elaboration and Characterization of ZnO Transition Metal (Co, Mn, Ni, Fe) Doped Aerogel Nanoparticles
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Elaboration and Characterization of ZnO Transition Metal (Co, Mn, Ni, Fe) Doped Aerogel Nanoparticles Lassaad El Mir1, Aroussi Ben Mahmoud1, H.Jurgen von Bardeleben2, and Jean-Louis Cantin3 1 Physique des Matériaux et des Nanomatériaux Appliquée à l'Environnement, Faculté des Sciences de Gabès, Gabès, 6072, Tunisia 2 INSP, CNRS Université Paris 6, 140, rue de Lourmel, Paris, 75015, France 3 Université Paris 6, Paris, 75015, France
ABSTRACT Nanocrystalline transition metal (TM=Co, Mn, Ni, Fe) doped zinc oxide powders have been elaborated by a new protocol based on slow hydrolyse of zinc acetate dissolved in methanol and supercritical drying in ethyl alcohol. The powders have a narrow size distribution with an average value of ~ 25nm. Electron microscopy characterization showed that the size of the ZnO:TM particles did not change significantly for the different dopants. High doping levels of up to [TM] =0.25 have been investigated. X-ray diffraction studies showed the formation of the ZnO wurtzite phase for all dopants but secondary phases are equally detected. High temperature ferromagnetism was observed for Ni and Co doped powders whereas Mn doped powders showed only antiferromagnetic interactions. EPR spectroscopy indicates that the magnetism is related to the presence of extrinsic phases. INTRODUCTION The magnetic properties of highly transition metal doped ZnO have been widely studied in the recent years due to the predicted room temperature ferromagnetic phases [1,2]. Most of the studies have been performed on thin films elaborated by pulsed laser deposition, sputtering or metalorganic chemical vapour deposition and the bulk properties of such films were investigated. Typical TM concentrations explored are between x=0.03 and x=0.3 and the possibility to produce such films free from secondary phase inclusions depends on the deposition conditions and the maximum solubility of the dopant. The experimental results obtained have been reviewed [3-5] and it can be concluded that in general for Co and Mn dopants with doping concentrations higher than x=0.05 antiferromagnetic nearest neighbour interactions dominate the magnetic properties of these n-type conductive films. Some reports of ferromagnetic interactions have been published for low doped films 0.02
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