摘要
采用量子力学计算软件包研究了单晶Heusler合金Ni2MnGa的结构参数、磁矩、四方变形以及磁性微观机理,并将计算结果与实验值和其它理论计算值进行了比较。计算所得的结构参数和磁矩相对于局域自旋密度近似值而言,与实验值符合得更好。四方变形中,发现磁矩在c/a=1附近有一个尖锐的最小值,在c/a≈0.94处有一个局域最大值,此磁矩的局域最大值对应着一个稳定的马氏体。总磁矩随c/a的变化主要来自Ni原子:由于一个原胞中有两个Ni原子对其总磁矩作了贡献,因而屏蔽了Mn原子的贡献所致。对总态密度的分析表明,自旋向上的态密度位于费米面以下,而自旋向下的态密度有两个主峰,分别位于费米面两侧,这是磁有序合金的一个典型特性。且合金磁性主要源于Mn原子的d-eg和d-t2g亚带,这与实验结果一致。
Structure parameters, magnetic moments, tetragonal distortions and magnetic microcosmic mechanisms of single crystal Ni2MnGa Heusler alloy were studied by the vienna abinitio simulation package （VASP）. The results show that the structure parameters and magnetic moments agree well with the available experimental data and are better than the local spin density approximation （LSDA） method results compared with the available experiment data and other theoretical values. By analyzing tetragonal distortions, there exists a sharp minimum value near c/a= 1 and a local maximum value at c/a≈0. 94, and this maximum value corresponds to a stable martensitic phase. In addition, the variation of the total magnetic moment with c/a is mainly due to the contribution of Ni atoms because the total magnetic moment is almost equally contributed by two Ni atoms of per formula unit, while the contribution of Mn atom is very small. By analyzing the total state density （DOS） of alloy, the state densities of maior peaks at the majority spin states are below the Fermi level. At the minority spin states, the two major peaks are separated by the Fermi level, which is the characteristic of stability for ferromagnetic ordered alloys. The magnetism of Ni2 MnGa alloy mainly originates from Mn atom, and the Mn moment in Ni2MnGa originates from its d-eg and d-t2g subbands, which agrees with the experimental results.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2005年第11期1843-1847,共5页
The Chinese Journal of Nonferrous Metals
基金
国家自然科学基金资助项目(50371026)
