Enhanced room-temperature ferromagnetism of Co-doped SnO2 nanostructures produced by the hydrothermal method

In this work, Co-doped SnO₂ powders were synthesized via a simple hydrothermal process without using any surfactants. A detailed microstructural analysis showed that incorporation of C (II) ions distorts the SnO₂ lattice. The unit cell volume becomes smaller as the nominal Co content increases. Neither segregated secondary phases nor the Co-rich clusters were detected. The particles of Co-doped SnO₂ self-assembled from low-dimensional building blocks and acquired a three-dimensional hierarchical structure. The dependencies of the magnetic characteristics of the synthesized Co-doped SnO₂ on the concentration of Co are nonlinear. The highest saturation magnetization (3.5 emu/g) of the flower-like structures was found in the material with a Co/SnO₂ mass ratio of 0.06. One of the reasons for the enhancement of room-temperature ferromagnetism in the Co-doped SnO₂ is an anisotropic growth of SnO₂ crystals in the presence of Co (II) ions, which serve as a structure-controlling agent for the growing crystals.