The mechanosynthesis of cubic γ-phase pure BiFeO3 and Ti4+-doped BiFeO3 nanocrystalline particles and their preliminary characterization with magnetic measurements and Mössbauer spectroscopy are reported. The BiFeO3 nanoparticles (5-40 nm) were prepared by heating a 48 h pre-milled 1:1 molar mixture of α-Bi2O3 and α-Fe2O3 at 400 °C for (1 h). Doping α-Fe2O3 in the initial mixture of reactants with Ti4+ was found to lead to the formation of Ti4+-doped BiFeO3 nanoparticles by milling the reactants for 32 h. The magnetization of the BiFeO3 nanoparticles is found to be tripled under a maximum external field of 1.35 T and their magnetic hardness increases by ∼15 times relative to those of the corresponding bulk. The Ti4+-doped BiFeO3 nanoparticles exhibit higher magnetization relative to the pure ones. These observations are related to the spiral modulated spin structure of the compound. The Mössbauer data show ∼12 % of the BiFeO3 nanocrystalline particles to be superparamagnetic having blocking temperatures of less than 78 K. The quadrupole shift values of the magnetic spectral component favor the cubic structural symmetry. These observations were mainly associated with possible collective magnetic excitations as well as transverse relaxation of canted surface spins. The Ti-doped BiFeO3 nanoparticles gave statistically-poor Mössbauer spectra with no signs of a superparamagnetic behavior.
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