摘要
通过第一性原理计算系统地研究了掺杂Ti含量对Ni_8Mn_(4-x)Ga_4Ti_x(x为单胞中掺杂Ti原子的个数,x=0、0.5、1、1.5和2)铁磁形状记忆合金相稳定性和磁性能的影响。根据能量最低原理,掺杂的Ti组元优先占据Ni_2MnGa合金中的Mn阵点。随着Ti含量的增加,顺磁奥氏体与铁磁奥氏体相的总能之差减小,从本质上导致了实验观察到的合金Curie温度(TC)的降低。随着Ti含量的逐渐增加,Fermi面以下自旋向上总电子态密度逐渐降低,而自旋向下的部分几乎不变,导致自旋向上与自旋向下的电子数之差减小,这是Ti含量增加而合金总磁矩降低的本质原因。本工作的计算结果对指导实验中的成分设计和开发新型磁控形状记忆合金具有重要意义。
The main purpose of the present work is to explore the influence of the Ti addition on crystal structure,phase stability,magnetic properties and electronic structures of the Ni8Mn4-xGa4Tix(x is the number of Ti atoms in a unit cell,x=0,0.5,1,1.5 and 2)alloys by first-principles calculations,aiming at providing the theoretical data and directions for developing high performance ferromagnetic shape memory alloys(FSMAs)in this alloy system.The formation energy results indicate that the doped Ti preferentially occupies the Mn sites in Ni2MnGa alloy.With the increase of Ti content,the optimized lattice parameter of the ferromagnetic austenite increases regularly.For the martensitic phase,the lattice parameter a increases while c decreases,leading to a decreased c/a ratio.The paramagnetic and ferromagnetic austenitic phases both become stable because their formation energies(Eform)gradually decrease with the increasing amount of Ti.The experimentally reported decrease in the Curie temperature with increasing Ti content is derived from the decrease of the total energy difference between the paramagnetic and the ferromagnetic austenite.The total magnetic moment is mainly contributed by Mn,while the magnetic moments of Ga and Ti are nearly zero.The total magnetic moment decreases notably when Mn is gradually substituted by Ti because the atomic magnetic moment of Ti is much less than that of Mn,which is in fair consistent with the experimental observations.The intensity of up-spin total density of state(DOS)decreased dramatically with the increase of the Ti content;whereas the change of the down-spin part below EFis not obvious.This feature gives rise to the decrease of the total magnetic moments in these alloys.The results of present work are particularly useful in guiding composition design and developing new type of magnetic shape memory alloy.
作者
白静
石少锋
王锦龙
王帅
赵骧
BAI Jing;SHI Shaofeng;WANG Jinlong;WANG Shuai;ZHAO Xiang(Key Laboratory for Anisotropy and Texture of Materials Ministry of Education,Northeastern University,Shenyang 110819,China;School of Resources and Materials,Northeastern University at Qinhuangdao,Qinhuangdao 066004,China;Hebei Provincial Laboratory for Dielectric and Electrolyte Functional Materials,Northeastern University at Qinhuangdao,Qinhuangdao 066004,China;Key Laboratory of Advanced Metal Materials and Forming Technology in Qinhuangdao,Northeastern University at Qinhuangdao,Qinhuangdao 066004,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第3期369-375,共7页
Acta Metallurgica Sinica
基金
国家自然科学基金项目Nos.51771044
51431005
51301036
国家高技术研究发展计划项目No.SS2015AA031803
中央高校基本科研业务费专项资金项目No.N130523001~~
