中国物理B ›› 2022, Vol. 31 ›› Issue (5): 56105-056105.doi: 10.1088/1674-1056/ac3986

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Alloying and magnetic disordering effects on phase stability of Co2 YGa (Y=Cr, V, and Ni) alloys: A first-principles study

Chun-Mei Li(李春梅), Shun-Jie Yang(杨顺杰), and Jin-Ping Zhou(周金萍)   

  1. College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China
  • 收稿日期:2021-06-24 修回日期:2021-10-14 出版日期:2022-05-14 发布日期:2022-04-09
  • 通讯作者: Chun-Mei Li,E-mail:cmli@synu.edu.cn E-mail:cmli@synu.edu.cn
  • 基金资助:
    This work was supported by the National Natural Science Foundation of China (Grant Nos.12174269,11674233 and 51301176),the China Postdoctoral Science Foundation (Grant Nos.2013M530133 and 2014T70264),and the Natural Science Foundation of Liaoning Province,China (Grant Nos.2019-MS-287 and L201602672).

Alloying and magnetic disordering effects on phase stability of Co2 YGa (Y=Cr, V, and Ni) alloys: A first-principles study

Chun-Mei Li(李春梅), Shun-Jie Yang(杨顺杰), and Jin-Ping Zhou(周金萍)   

  1. College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China
  • Received:2021-06-24 Revised:2021-10-14 Online:2022-05-14 Published:2022-04-09
  • Contact: Chun-Mei Li,E-mail:cmli@synu.edu.cn E-mail:cmli@synu.edu.cn
  • About author:2021-11-15
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (Grant Nos.12174269,11674233 and 51301176),the China Postdoctoral Science Foundation (Grant Nos.2013M530133 and 2014T70264),and the Natural Science Foundation of Liaoning Province,China (Grant Nos.2019-MS-287 and L201602672).

摘要: The alloying and magnetic disordering effects on site occupation, elastic property, and phase stability of Co$_{2}Y$Ga ($Y={\rm Cr}$, V, and Ni) shape memory alloys are systematically investigated using the first-principles exact muffin-tin orbitals method. It is shown that with the increasing magnetic disordering degree $y$, their tetragonal shear elastic constant $C'$ (i.e., $(C_{11}-C_{12})/2$) of the $L2_{1}$ phase decreases whereas the elastic anisotropy $A$ increases, and upon tetragonal distortions the cubic phase gets more and more unstable. Co$_{2}$CrGa and Co$_{2}$VGa alloys with $y\geq0.2$ thus can show the martensitic transformation (MT) from $L2_{1}$ to $D0_{22}$ as well as Co$_{2}$NiGa. In off-stoichiometric alloys, the site preference is controlled by both the alloying and magnetic effects. At the ferromagnetism state, the excessive Ga atoms always tend to take the $Y$ sublattices, whereas the excessive Co atom favor the $Y$ sites when $Y={\rm Cr}$, and the excessive $Y$ atoms prefer the Co sites when $Y={\rm Ni}$. The Ga-deficient $Y={\rm V}$ alloys can also occur the MT at the ferromagnetism state by means of Co or V doping, and the MT temperature $T_{\rm M}$ should increase with their addition. In the corresponding ferromagnetism $Y={\rm Cr}$ alloys, nevertheless, with Co or Cr substituting for Ga, the reentrant MT (RMT) from $D0_{22}$ to $L2_{1}$ is promoted and then $T_{\rm M}$ for the RMT should decrease. The alloying effect on the MT of these alloys is finally well explained by means of the Jahn-Teller effect at the paramagnetic state. At the ferromagnetism state, it may originate from the competition between the austenite and martensite about their strength of the covalent banding between Co and Ga as well as $Y$ and Ga.

关键词: first-principles, martensitic transformation, elastic modulus, magnetic ordering, shape memory alloys

Abstract: The alloying and magnetic disordering effects on site occupation, elastic property, and phase stability of Co$_{2}Y$Ga ($Y={\rm Cr}$, V, and Ni) shape memory alloys are systematically investigated using the first-principles exact muffin-tin orbitals method. It is shown that with the increasing magnetic disordering degree $y$, their tetragonal shear elastic constant $C'$ (i.e., $(C_{11}-C_{12})/2$) of the $L2_{1}$ phase decreases whereas the elastic anisotropy $A$ increases, and upon tetragonal distortions the cubic phase gets more and more unstable. Co$_{2}$CrGa and Co$_{2}$VGa alloys with $y\geq0.2$ thus can show the martensitic transformation (MT) from $L2_{1}$ to $D0_{22}$ as well as Co$_{2}$NiGa. In off-stoichiometric alloys, the site preference is controlled by both the alloying and magnetic effects. At the ferromagnetism state, the excessive Ga atoms always tend to take the $Y$ sublattices, whereas the excessive Co atom favor the $Y$ sites when $Y={\rm Cr}$, and the excessive $Y$ atoms prefer the Co sites when $Y={\rm Ni}$. The Ga-deficient $Y={\rm V}$ alloys can also occur the MT at the ferromagnetism state by means of Co or V doping, and the MT temperature $T_{\rm M}$ should increase with their addition. In the corresponding ferromagnetism $Y={\rm Cr}$ alloys, nevertheless, with Co or Cr substituting for Ga, the reentrant MT (RMT) from $D0_{22}$ to $L2_{1}$ is promoted and then $T_{\rm M}$ for the RMT should decrease. The alloying effect on the MT of these alloys is finally well explained by means of the Jahn-Teller effect at the paramagnetic state. At the ferromagnetism state, it may originate from the competition between the austenite and martensite about their strength of the covalent banding between Co and Ga as well as $Y$ and Ga.

Key words: first-principles, martensitic transformation, elastic modulus, magnetic ordering, shape memory alloys

中图分类号:  (Alloys )

  • 61.66.Dk
62.20.de (Elastic moduli) 63.20.dk (First-principles theory)