Synthesis and magnetic properties of ε-Fe2O3 by ball milling and post annealing

Abstract A novel method for synthesizing e-Fe2O3 nanoparticles was proposed. The e-Fe2O3 nanoparticles were prepared by ball milling of Iron(III) nitrate nonahydrate and hydrophilic vapor phase nano-silica and post annealing. The structure, morphology and magnetic properties of the prepared nanoparticles were studied by X-ray diffraction,Raman spectroscopy, transmission electron microscopy, and magnetic measurements. The results show that the average particle size and magnetic properties of the e-Fe2O3 nanoparticles can be controlled by the relative amount of Iron(III) nitrate nonahydrate used. With the increase of the amount of Iron(III) nitrate nonahydrate, the e-Fe2O3 nanoparticle size increases. And the coercivity of the e-Fe2O3 nanoparticles increases. The magnetic hysteresis loops of the e-Fe2O3 nanoparticles show clear shifts along the magnetic field axis at 300K, after the nanoparticles were warmed from low temperature in a magnetic field of 50 kOe. This observation is explained in term of exchange bias effect.