Atomic-Scale Investigation of SmCo5/α-Fe Nanocomposites: Influence of Fe/Co Interdiffusion on the Magnetic Properties

The nanostructure of SmCo5/alpha-Fe nanocomposites elaborated by high-energy ball milling was investigated using atom probe tomography. This high-resolution technique allowed obtaining in the real space a 3D mapping of the chemical species (Sin, Co, and Fe) on the atomic scale. 3D reconstructions of the nanostructure of the analyzed samples were realized from the data and show that the majority of the SmCo5/alpha-Fe nanocomposite is composed of alpha-Fe(Co) soft magnetic nanosized crystallites embedded in a Srn-(Co,Fe) hard magnetic matrix. These results confirm the formation of the alpha-Fe(Co) phase and the contamination of the initial Sin Cos by Fe atoms. The interfaces between the alpha-Fe(Co) soft magnetic phase and the Srn-(Co,Fe) hard magnetic phase were also chemically analyzed on the atomic scale. Large graded interfaces were evidenced. Monte Carlo simulations assuming a linear variation of the anisotropy in the intermixed interface between the interdiffusion can lead to an increase in the coercive field. Sm-(Co,Fe) and the Fe(Co) regions indicate that the Fe/Co interdiffusion can lead to an increase in the coercive field.