Mechanosynthesis and magnetic properties of nanocrystalline LaFeO3 using different iron oxides

The synthesis of the orthoferrite LaFeO3 using high-energy ball-milling of La2O3 and Fe3O4 or α-Fe2O3 oxides and subsequent thermal treatments of resulting powders was studied. The phase evolution during the mechanical treatment was analyzed by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Also, magnetic properties of the obtained materials were measured at room temperature by vibrating sample magnetometry (VSM). From 30 min of mechanochemical activation the gradual disappearance of reactants and the formation of LaFeO3 were observed. For both reactive mixtures the reaction was completed after 3 h of milling. Magnetic hysteresis loops of these mechanoactivated samples showed a significant ferromagnetic component in LaFeO3. This behavior was interpreted on the basis of a spin-canting effect induced by the mechanochemical treatment. Thermal treatments allowed the relaxation of the distorted structure, resulting in the formation of the conventional antiferromagnetic LaFeO3 phase.