Mechanosynthesis, magnetic and Mössbauer characterization of pure and Ti4+-doped cubic phase BiFeO3 nanocrystalline particles (original) (raw)

The mechanosynthesis of cubic γ -phase pure BiFeO 3 and Ti 4+ -doped BiFeO 3 nanocrystalline particles and their preliminary characterization with magnetic measurements and Mössbauer spectroscopy are reported. The BiFeO 3 nanoparticles (5-40 nm) were prepared by heating a 48 h pre-milled 1:1 molar mixture of α-Bi 2 O 3 and α-Fe 2 O 3 at 400 • C for (1 h). Doping α-Fe 2 O 3 in the initial mixture of reactants with Ti 4+ was found to lead to the formation of Ti 4+ -doped BiFeO 3 nanoparticles by milling the reactants for 32 h. The magnetization of the BiFeO 3 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 Ti 4+ -doped BiFeO 3 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 BiFeO 3 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 BiFeO 3 nanoparticles gave statistically-poor Mössbauer spectra with no signs of a superparamagnetic behavior.