Abstract: The electronic structure and magnetic properties of Mn-doped Fe2-x Mnx Si systems have been calculated by the first-principles pseudo-potential method based on density functional theory ( DFT) .The results show that the Mn-doped Fe2-x Mnx Si system is a ferromagnet with different ratios of Mn , the half-metallic gap of undoped Fe2Si is 0.164 eV.When the doping ratio is 8.3;, the spin-down part is transformed into the direct bandgap semiconductors of L .The Fe2-x MnxSi (x=0.17) system exhibits half-metallic properties .When the doping ratio is 12 .5;, the spin-down part is transformed into the direct bandgap semiconductor of A, and the Fe2-x MnxSi (x =0.25) system exhibits half-metallic properties .The system is transformed into metal when the doping ratio is 25;.Mn-doped makes the band structure and electron density of Fe 2-x Mnx Si systems move in the low energy direction , and the Fermi level falls into the spin-down band gap , which makes the spin polarization rate reach 100;.The half-metallic and magnetic properties of Fe 2-x Mn x Si systems are mainly derived from the d-d exchange between Fe-3d and Mn-3d electrons, p-d hybridization between Si-3p and Fe-3d electrons.The results provide effective theoretical guidance for the electromagnetic control of half-metallic ferromagnet Fe 2 Si.

Key words: The electronic structure and magnetic properties of Mn-doped Fe2-x Mnx Si systems have been calculated by the first-principles pseudo-potential method based on density functional theory ( DFT) .The results show that the Mn-doped Fe2-x Mnx Si system is a ferromagnet with different ratios of Mn , the half-metallic gap of undoped Fe2Si is 0.164 eV.When the doping ratio is 8.3;, the spin-down part is transformed into the direct bandgap semiconductors of L .The Fe2-x MnxSi (x=0.17) system exhibits half-metallic properties .When the doping ratio is 12 .5;, the spin-down part is transformed into the direct bandgap semiconductor of A, and the Fe2-x MnxSi (x =0.25) system exhibits half-metallic properties .The system is transformed into metal when the doping ratio is 25;.Mn-doped makes the band structure and electron density of Fe 2-x Mnx Si systems move in the low energy direction , and the Fermi level falls into the spin-down band gap , which makes the spin polarization rate reach 100;.The half-metallic and magnetic properties of Fe 2-x Mn x Si systems are mainly derived from the d-d exchange between Fe-3d and Mn-3d electrons, p-d hybridization between Si-3p and Fe-3d electrons.The results provide effective theoretical guidance for the electromagnetic control of half-metallic ferromagnet Fe 2 Si.