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采用基于密度泛函理论的第一性原理方法,对新型Heusler合金RuMn_2 Sn的晶体结构、电子结构、磁性、四方变形等性质进行了系统的研究.研究结果表明:1)在奥氏体态下,磁性原子Mn对体系总磁矩的贡献最大,其中Mn(A)和Mn(B)原子磁矩的值不等并且呈反平行耦合,导致RuMn_2 Sn具有稳定的亚铁磁基态,该结果与实验一致;2)由XA型立方结构至四方结构的四方变形中,发现c/a约为1.23处存在一个能量更低的稳定的马氏体相,其呈现反铁磁的特性;3)在奥氏体态和马氏体态下,Mn(A)和Mn(B)原子之间弱的d-d直接交换作用是维持它们之间亚铁磁和反铁磁耦合的主要原因.根据上述计算结果,预测RuMn_2 Sn具有良好的磁性形状记忆效应.
The first-principle method based on density functional theory (DFT) was used to systematically study the crystal structure, electronic structure, magnetism and tetragonal deformation of new Heusler alloy RuMn_2 Sn.The results show that: 1) In the austenitic state , And the contribution of Mn to the total magnetic moment of the system is the largest. The values of magnetic moments of Mn (A) and Mn (B) atoms are unequal and anti-parallel coupled, resulting in a stable ferrimagnetic ground state of RuMn_2 Sn. Experimentally; 2) From tetragonal deformation of the XA-type cubic structure to the tetragonal structure, it is found that there exists a stable martensite phase with a lower energy at c / a of about 1.23, which exhibits antiferromagnetic properties; 3) The weak direct dd exchange between Mn (A) and Mn (B) atoms in austenite and martensite is the main reason for maintaining the ferromagnetic and antiferromagnetic coupling between them.According to the above results, It is predicted that RuMn_2 Sn has a good magnetic shape memory effect.