First Principles Study On The Bcc And Fcc Structure Of Fe_1-xT_x?T=Cr,Mn,Co,Ni?Alloys

The magnetic state of the transition metal ?magnetic order? is closely related to its crystal structure. The ground state of Fe is bcc structure with ferromagnetic order ?a phase?, but the low temperature fcc structure ?? phase? is antiferromagnetic. It is found that the lattice structure of metallic Fe thin film as well as the related the magnetic order can be controlled by an electric field. Alloying is an effective way to control the structure and magnetic properties of transition metals. Therefore, the study on stability and magnetic properties of fcc and bcc structures of FeT alloy is of great practical significance.The ground state properties of a, y phases of Fe_1-xT_x?T=Cr, Mn, Co, Ni? alloys are studied by the first principles approach. The concentration dependence of lattice parameters, local magnetic configuration and the relative stability of a, ? phases are addressed. It was found that the alloying concentration dependence of the lattice parameters, magnetic moment, bulk modulus and atomic energy of a,? phases Fe_1-xT_x alloys is very different from each other, implying that the dilute alloying of Fe with transition metals T ?T =Cr, Mn, Co, Ni? display a complicated correlation among structure, magnetism and concentration. ?-Fe_1-xT_x alloys keep the ferromagnetism and stability of a-Fe. it demonstrates that the stability of alloys system is weakly impacted by the lattice deformation:A small lattice distortion along c axis, namelv a variation of c/a, could lead to a large increase in energy and a decrease of magnetic moment. This fact suggests that the tetragonality of ?-Fe_1-xT_x is originated from the antiferromagnetism. And this antiferromagnetic ? phase is still a metastable phase. Under lattice strain, the energy difference ??E=?Ebcc-?Efcc? between bcc and fcc phases of Fe_1-xT_x alloy is larger than zero, indicating that the fcc structure of the alloy under lattice strain is more stable than the bcc structure, while doping concentration x affects both bcc and fcc structure of Fe_1-xT_x alloys differently under lattice strain.