Effect of Annealing on the Structure and Magnetic Properties of CoMnSi

This paper reports a comparative study of the magnetization, magnetocaloric effects, and crystal lattices of an as-cast sample and an annealed sample of the CoMnSi compound. Magnetic measurements showed that the annealed sample has high magnetization and a doubled maximum magnetic entropy change with respect to the as-cast sample. X-ray diffraction studies determined that both samples crystallize into an orthorhombic lattice. However, there are remarkable differences in the lattice parameters and one of the nearest Mn-Mn distances between the samples. Spectroscopic measurements of the X-ray absorption near-edge structure revealed that Co-Si bonds of the annealed sample are shorter than those of the as-cast sample due to stronger p-d hybridization of Co and Si atoms, while other chemical bonds do not show any difference. It is concluded that high-temperature annealing enhances ferromagnetic interactions in the lattice of CoMnSi by chemical ordering of Co atoms.