Magnetic Properties of Nanostructured MnFe2O4 Synthesized by Precursor Technique
摘要:
Nanostructured MnFe2O4 particles in the size range 7-30 nm are prepared by the thermal decomposition of manganese iron citrate precursor at different temperatures (623-973 K) in an inert atmosphere. The Curie temperature (T-C) of the as-prepared MnFe2O4 nanosized particles is found to be higher than the bulk material by 70 K. This is explained on the basis of non-equilibrium cation distribution in our samples. The heat treatment of the particles at 673 K changes the cation distribution to an equilibrium state and correspondingly T-C is modified. We observe that saturation magnetization decreases with decrease in the size of the particles and this is explained by a magnetic dead layer present on the surface of the nanostructured particles.
The effect of Fe doping in the Mn site on the magnetic, transport and structural properties of polycrystalline La1,2Ca1,2MnO3 was studied. Doping with low Fe concentration (< 10%) strongly affects electrical transport and magnetization. Long range charge order is disrupted even for the lowest doping level studied (similar to2%). For Fe concentration up to 5% a ferromagnetic state develops at low temperature with metallic-like conduction and thermal hysteresis. In this range. the Curie temperature decreases monotonously as a function of Fe doping. Insulating behavior and a sudden depression of the ferromagnetic state is observed by further Fe doping. (C) 2001 Elsevier Science B.V. All rights reserved.