掺杂Bi促进L1_(0)-FePt有序转变的第一性原理研究  

Study on Ordering Transition of L1_(0)-FePt Promoted by Doping Bi with First Principles

作　　者：刘传值 赵东 王群首 郑健 孟祥颖[2] 徐民 裴文利 Liu Chuanzhi;Zhao Dong;Wang Qunshou;Zheng Jian;Meng Xiangying;Xu Min;Pei Wenli(School of Materials Science and Engineering,Northeastern University,Shenyang 110819,China;College of Sciences,Northeastern University,Shenyang 110819,China)

机构地区：[1]东北大学材料科学与工程学院,辽宁沈阳110819 [2]东北大学理学院,辽宁沈阳110819

出　　处：《稀有金属材料与工程》2022年第10期3699-3706,共8页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(52071070,51871045);中央高校基本科研业务费专项资金(N2017003,N2102004)。

摘　　要：掺杂第三元素是促进FePt有序相变和降低有序转变温度的重要方法,元素Bi可大幅度降低有序转变温度,在低温下直接合成出高有序的FePt纳米粒子,但Bi促进FePt有序的机理和有序转变中的作用仍然是一个挑战。本工作针对该问题,基于第一性原理密度泛函理论研究了Bi元素对FePt的晶格常数、形成能、差分电荷密度、饱和磁化强度和有序转变温度的影响。结果表明Bi原子取代Fe原子比取代Pt原子的替位形成能更低,Bi原子更容易取代Fe原子。Bi原子取代近邻位的替位形成能要比远邻位的替位形成能更低,Bi原子倾向于在FePt晶格内聚集。Fe原子是FePt体系磁性的主要来源,Bi原子在Pt格位对FePt的电子结构和磁性影响很小。掺杂Bi元素后FePt的有序转变温度明显降低,双格位取代时FePt体系的有序转变温度最低为623.32 K,掺杂位置比掺杂浓度对有序转变温度的影响更大。空位机制在有序转变中起主导作用,Bi元素降低了FePt的空位形成能,提高体系中Fe原子和Pt原子的空位浓度并促进Fe原子和Pt原子的扩散和迁移,从而促进FePt有序相变。Doping the third element is an important method to promote ordering transition of FePt and reduce the ordering transition temperature.Bi can greatly reduce the ordering transition temperature and directly synthesize highly ordered FePt nanoparticles at low temperature,but the mechanism of Bi promoting FePt ordering and the role in ordering transition remain a challenge.Therefore,this work investigated the effects of Bi element on the lattice constant,formation energy,differential charge density,saturation magnetization and ordering transition temperature of FePt with the first principle density functional theory.The results show that the substitution formation energy of Bi atom replacing Fe atom is lower than that of Pt atom.Bi atom is easier to replace Fe atom.The substitution formation energy of Bi atoms replacing near neighbors is lower than that of far neighbors.Bi atoms tend to aggregate in the lattice.Fe atoms are the main source of magnetism in FePt systems,and Bi atoms have little effect on the electronic structure and magnetic properties of FePt at the Pt lattice site.The ordering transition temperature of FePt is significantly reduced after the doping of Bi element.The lowest ordering transition temperature of the FePt system is 623.32 K under double-site substitution.The doping position has greater influence on the ordering transition temperature than the doping concentration.The vacancy mechanism plays a leading role in the ordering transition.Bi element reduces the vacancy formation energy of FePt,increases the vacancy concentration of Fe and Pt atoms in the system,and promotes the diffusion and migration of Fe and Pt atoms,so as to promote the ordering transition of FePt.

关 键 词：L10-FePt SQS 形成能 有序转变温度 

分 类 号：TG146.3[一般工业技术—材料科学与工程]