Ga含量对Mn_(2-x)NiGa_(1+x)结构和磁性的影响  

Influences of Ga content on the structure and magnetic properties of Mn_(2-x)NiGa_(1+x) alloys

作　　者：刘红艳[1] 柳祝红[1] 李歌天[1] 马星桥[1] 

机构地区：[1]北京科技大学物理系,北京100083

出　　处：《物理学报》2016年第4期323-329,共7页Acta Physica Sinica

基　　金：第四十四批教育部留学回国人员启动基金;中央高校基本科研业务费专项资金(批准号:FRF-BR-14-025A)资助的课题~~

摘　　要：系统研究了铁磁性形状记忆合金Mn_(2-x)NiGa_(1+x)的结构、磁性和有序化转变.研究表明:随着Ga含量的增加,Mn_(2-x)NiGa_(1+x)的母相结构由Hg_2CuTi型逐渐转变到Cu_2MnAl型Heusler结构.母相的晶格常数先增加后降低,当x=0.3时达到最大值.0.3 x 0.8时,材料除呈现Heusler结构的主相之外,还出现了Ni_2In型六角相.过渡金属中3d电子之间交换相互作用的减弱,导致Mn_(2-x)NiGa_(1+x)主相的居里温度由Mn_2NiGa的590 K逐渐降低至Ga_2MnNi的220 K左右;当x=0.6—0.8时,Ni_2In型六角相的居里温度与主相的居里温度出现分离.Ga对Mn的替代引起合金中原子间耦合作用的变化,导致低温下Mn_(2-x)NiGa_(1+x)的饱和磁化强度先增加后降低,即x 0.4时呈上升趋势,x>0.4时急剧下降.差热分析结果显示,随着x从0增加到1,样品熔化温度逐渐降低,B2相到Heusler相的转变温度先降低后增加.The structure magnetism and ordering transition of the ferromagnetic shape memory alloy Mn2-xNiGa1＋x have been systematically studied in this paper. With increasing Ga content, the structure of the parent phase Mn2-xNiGa1＋x is transformed from Hg2CuTi-type to Cu2MnAl-type Heusler alloy gradually. Its lattice constant increases first and then decreases, reaching its maximum at x = 0.3. The sample displays both the primary phase of Heusler and the Ni2In-type hexagonal phase in precipitate form when x lies in the range of 0.3-0.8. The Curie temperature of the primary phase of Heusler alloy Mn2_xNiGal＋x reduces gradually from 590 K for Mn2NiGa to about 220 K for Ga2MnNi with the decrease of the exchange interaction between 3d electrons in the transition metals. However, the variation of Curie temperature of Ni2In-type hexagonal phase is gentle. The separation of Curie temperatures between the Ni2In-type hexagonal phase and the primary phase of Heusler occurs when x lies in the range from 0.6 to 0.8. Substitution of Mn by Ga has a significant influence on the coupling interaction among various atoms, lending to first increasing and then decreasing of the saturated magnetization of Mn2-xNiGa1＋x at low temperatures. That is, the saturated magnetization will rise for x ≤ 0.4 and drops sharply for x 〉 0.4. Results of differential scanning calorimeter show that the melting temperature decreases gradually as x increases. Meanwhile, the transition temperature from parent phase （B2） to Heusler phase decreases first and increases later.

关 键 词：铁磁形状记忆合金 结构转变 磁性 MnNiGa 

分 类 号：O482.5[理学—固体物理]