Electronic Structure,Synthesis And Atom Occupation Of Heusler Alloys Containing Low-valence Transition Elements

Heusler alloys are rich in physical property.Previous investigations on Heuser alloys focused mainly on the alloys containing two transition metals of group seven,eight or Cu and found many functional properties.In my study,Heusler alloys containing low-valence transition metals,especially Zr,Sc,Y and Cr atoms,have been investigated systematically in theory and experiment.In this work,we first fouse on ZrFeVZ?Z=Al,Ga,In?alloys as our research object.By using the first-principle calculations,we have systematically investigated band gap,electronic structures and magnetic properties of quaternary Heusler alloys ZrFeVZ?Z=Al,Ga,In?.It found that ZrFeVZ?Z=Al,Ga,In?are half-metallic ferrimagnets at their equilibrium lattice constants and retain a high spin polarization in a quite wide range of lattice distortions.The total magnetic moment is 2?_B per unit cell for ZrFeVZ?Z=Al,Ga,In?alloys follows the Slater–Pauling rule with the total number of valence electrons minus 18.Using first-principle calculations we study the electronic and magnetic properties of FeMnScZ?Z=Al,Ga,In?using GGA and GGA+U methods.It was shown that FeMnScZ?Z=Al,Ga,In?alloys are half-metallic materials at their equilibrium lattice constants with both methods.More importantly,the double-degenerate states in spin-up channel shift above the triple-degenerate states using GGA+U method.The electronic structure of FeMnScAl alloy doping main-group elements,transition elements and the case of adding different hydrostatic strains are also discussed in detail.We study the electronic structures and magnetic properties for Cr₂MnZ?Z=Al,Ga,In?alloys.It is found that the order of e_u and t_1u states are inverted in Cr₂MnZ?Z=Ga,In?alloys,which compare to Cr₂MnAl alloy.The electronic structures and magnetic properties for Cr_1.75Fe_0.25MnZ?Z=Al,Ga,In?and Cr₂MnAl_1-xGa_x?x=0.25,0.5,0.75?alloys are also discussed.Finally single-phase Cr₂MnAl_1-xGa_x?x=0,0.25,0.5,0.75?series alloys with b.c.c structure was synthesized after annealing treatment.We study the influence of doping elements on YPdBi,using first principles of the LDA,GGA and MBJLDA three approximate calculation methods.Without considering the spin-orbit coupling by adjusting the composition of alloys can be induced to form the topological insulators.We consider this is due to the scalar relativistic effects of the atom.Through the LDA and GGA,MBJLDA three approximate calculation methods,we find that the MBJLDA approach is most demanding to identify a topological insulator and the LDA approach shows higher band inversion strength than GGA.