Research On Elements-doped L2₁-type Ni-Mn-Ge: First-principles Study

With the development of technology, the new materials properties of erospace, communications, automotive, computer, control and other areas of computing performance is increasing. Therefore it is urgently needed for research and develop new functional materials. Previous studies found that the non-stoichiometric Ni2 Mn Ga have physical properties sucha as large magnetic induced strain and super-elastic property. However, due to the relatively brittle, together with low phase temperature and the Curie temperature factors, the application of Ni-Mn-Ga alloys is little used in industry. As a member of ferromagnetic shape memory alloy, Ni2 Mn Ge has the same crystal structure as the L21 type with Ni2 Mn Ga. This paper tries to analyze the the non-stoichiometric Ni2 Mn Ge, which might develop new functional materials.Based on the density functional theory, this paper used the CASTEP software package of Materails Studio6.0 program, and to simulate Ni2+xMn1-xGe compounds. When x=0, 0.25, 0.5, the crystal structure of the Ni2+ xMn1-xGe 1×1×5 supercell geometry optimized, calculat the lowest energy band structure and density of states. In addition, When x = 0, 0.25, 0.5, 1, Ni2 Mn Ge1-xSix with 1×1×5 supercell geometry are also optimized, calculating the lowest energy band structure and density of states.With the doped concentration of Ni atoms increasing, L21 type Ni2 +xMn1-xGe(x=0,0.25,0.5) in the density of states near the Fermi surface are not zero, therefore, L21 type Ni2 + xMn1-xGe(x = 0,0.25,0.5) belong to the metallic; With the doped concentration of Ni atoms increasing, L21 type Ni2+xMn1-xGe(x=0,0.25,0.5) magnetic gradually decreased, and the magnetic main contribution of d states of Mn; With the doped concentration of Ni atomsincreasing, L21 type Ni2 + xMn1-xGe(x=0,0.25,0.5) are present p-d hybrid effect, and the role of hybridization gradually decreased; With the doped concentration of Si atoms increasing, L21 type Ni2 Mn Ge1-xSix(x = 0.25,0.5,1) in the density of states near the Fermi level are nonzero, therefore, L21 type Ni2 Mn Ge1-xSix(x=0.25,0.5,1) belong to the metallic; With the doped concentration of Si atoms increasing, L21 type Ni2 Mn Ge1-xSix(x=0.25,0.5,1) magnetic gradually decreased, and the magnetic main contribution of d state of Mn; Ni2 Mn Ge1-xSix(x=0.25, 0.5, 1) are ferromagnetic; With Si atomic doped concentration increases, L21 type Ni2 Mn Ge1-xSix(x=0.25,0.5,1) are present p-d hybrid effect, and the role of hybridization gradually decreased.