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arXiv 1603.09112cond-mat.mtrl-sci
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Ni基和Co基全Heusler合金中马氏体转变和半金属度共存可能性的从头算研究

Probing the possibility of coexistence of martensite transition and half-metallicity in Ni and Co-based full Heusler Alloys : An ab initio Calculation

Tufan Roy, Dhanshree Pandey, Aparna Chakrabarti

摘要:

采用基于密度泛函理论的第一性原理计算方法,研究了Heusler合金Ni $_{2}BC$和Co $_{2}BC$($B$ = Sc、Ti、V、Cr、Mn以及Y、Zr、Nb、Mo、Tc; $C$ = Ga、Sn)的力学、电学和磁学性质。在电子结构(态密度)和力学性质(四轴剪切常数)以及磁相互作用(海森堡交换耦合参数)的基础上,我们详细探讨了这些材料的性质。我们计算了这些合金在(面心)立方奥氏体结构中的形成能,以探讨所有这些材料的稳定性。从能量的角度来看,我们已经研究了电子稳定的合金的可能性,有一个tetraquinone相的能量低于相应的立方相。大量的磁性合金被发现具有立方相作为它们的基态。另一方面,对于另一类合金,已经发现四元相与立方相相比具有较低的能量。此外,我们发现四重态剪切常数的值显示出一致的趋势:对于不倾向于四重态转变的材料,四重态剪切常数的值为高正值,而对于其他材料,四重态剪切常数的值为低或负值。在文献中,已经看到经历马氏体转变的材料被发现本质上是金属的。我们在这里探测是否有任何Heusler合金,它有一个倾向,进行四重态转变,并在同一时间拥有一个高自旋极化在费米能级。从我们的研究中发现,在表现出马氏体相作为其基态的四种材料中,其中三种材料,即Ni $_{2}$ MnGa、Ni $_{2}$ MoGa和Co $_{2}$ NbSn具有金属性质;相反,Co $_{2}$ MoGa表现出高自旋极化。

英文摘要:

Using first-principles calculations based on density functional theory, we have studied the mechanical, electronic, and magnetic properties of Heusler alloys, namely, Ni$_{2}BC$ and Co$_{2}BC$ ($B$ = Sc, Ti, V, Cr and Mn as well as Y, Zr, Nb, Mo and Tc; $C$ = Ga and Sn). On the basis of electronic structure (density of states) and mechanical properties (tetragonal shear constant), as well as magnetic interactions (Heisenberg exchange coupling parameters), we probe the properties of these materials in detail. We calculate the formation energy of these alloys in the (face-centered) cubic austenite structure to probe the stability of all these materials. From the energetic point of view, we have studied the possibility of the electronically stable alloys having a tetragonal phase lower in energy compared to the respective cubic phase. A large number of the magnetic alloys is found to have the cubic phase as their ground state. On the other hand, for another class of alloys, the tetragonal phase has been found to have lower energy compared to the cubic phase. Further, we find that the values of tetragonal shear constant show a consistent trend : a high positive value for materials not prone to tetragonal transition and low or negative for others. In the literature, materials, which have been seen to undergo the martensite transition, are found to be metallic in nature. We probe here if there is any Heusler alloy which has a tendency to undergo a tetragonal transition and at the same time possesses a high spin polarization at the Fermi level. From our study, it is found that out of the four materials, which exhibit a martensite phase as their ground state, three of these, namely, Ni$_{2}$MnGa, Ni$_{2}$MoGa and Co$_{2}$NbSn have a metallic nature; on the contrary, Co$_{2}$MoGa exhibits a high spin polarization.

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