Structures, phase transitions, and magnetic properties of Co3Si from first-principles calculations
AbstractCo3Si was recently reported to exhibit remarkable magnetic properties in the nanoparticle form [B. Balasubramanian , Appl. Phys. Lett. 108, 152406 (2016)]10.1063/1.4945987, yet better understanding of this material should be promoted. Here we report a study on the crystal structures of Co3Si using an adaptive genetic algorithm and discuss its electronic and magnetic properties from first-principles calculations. Several competing phases of Co3Si have been revealed from our calculations. We show that the hexagonal Co3Si structure reported in experiments has lower energy in the nonmagnetic state than in the ferromagnetic state at zero temperature. The ferromagnetic state of the hexagonal structure is dynamically unstable with imaginary phonon modes and transforms into a new orthorhombic structure, which is confirmed by our structure searches to have the lowest energy for both Co3Si and Co3Ge. Magnetic properties of the experimental hexagonal structure and the lowest-energy structures obtained from our structure searches are investigated in detail.