Nanocrystalline ferrites prepared by mechanical activation and mechanosynthesis

At present, the high-energy milling method becomes widely used for the preparation of nanocrystalline materials due to its relative simplicity and availability. In this research report, selected examples are presented of the preparation of nanoscale spinel ferrites by mechanical activation and mechanosynthesis. Nanosized particles of mechanochemically prepared spinel ferrites are structurally and magnetically disordered due to the non-equilibrium cation distribution and non-collinear spin arrangement. As a consequence, they exhibit interesting physical and chemical properties markedly different from those of their bulk counterparts. Several interesting features are involved in the work, e.g., superparamagnetism, an enhanced chemical reactivity, an irreversible magnetic behaviour, an enhanced magnetic ordering temperature, and an altered (reduced or enhanced) saturation magnetization in comparison with the corresponding bulk materials. Taking into account the considerable relevance of the thermal stability of nanoscale complex oxides to nanoscience and nanotechnology, results on the response of mechanochemically prepared spinet ferrites to changes in temperature will also be presented.