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采用第一性原理的全势能线性缀加平面波方法, 对semi-Heusler合金CoCrTe和CoCrSb 的电子结构进行自旋极化计算. CoCrTe和CoCrSb处于平衡晶格常数时是半金属性铁磁体, 其半金属隙分别为0.28和0.22 eV, 晶胞总磁矩为3.00 B和2.00 B. CoCrTe和CoCrSb的晶胞总磁矩主要来自于Cr原子磁矩. Co, Te和Sb的原子磁矩较小, 它们的磁矩方向与Cr原子的磁矩方向相反. 使晶格常数在 13%的范围内变化(相对于平衡晶格常数), 并计算CoCrTe 和CoCrSb 的电子结构. 计算研究表明, CoCrTe和CoCrSb的晶格常数变化分别在-11.4%-9.0%和-11.2%-2.0%时仍具有半金属性, 并且它们晶胞总磁矩稳定于3.00 B 和2.00 B.Half-metallic ferromagnet, in which the electrons with one spin band are metallic and the electrons with another spin band are semiconducting, is believed to be the most promising spin-injector material for spintronic devices, such as spin valves, spin filters, spin diodes, and magnetic tunnel junctions. The main advantages of half-metallic Heusler alloy over other half-metallic systems are their relatively high Curie temperatures and structural similarity to important binary semiconductors that are widely utilized in the industry. Thus far, half-metallicity has been predicted theoretically or confirmed experimentally in a limited number of Heusler alloys. Exploring new half-metallic Heusler alloys is necessary. In this study, the full-potential linearized augmented plane wave (FP_LAPW) method under density functional theory is utilized to investigate the electronic structures and magnetisms of semi-Heusler alloys CoCrTe and CoCrSb. In the calculations, the generalized gradient approximation (GGA) in the scheme of Perdew-Bueke-Ernzerhof is adopted to treat the exchange-correlation potential. The cutoff parameter is set to be Rmt Kmax =9, where Rmt is the smallest atomic sphere radius and Kmax is the maximum value of the reciprocal lattice vector. Meshes (131313 k-points) are used in the first Brillouin zone integration. Self-consistent calculations are considered to be convergent only when the integrated charge difference between the last two iterations is less than 110-4 e/cell. Spin-polarized calculations of the electronic structure for the semi-Heusler alloys CoCrTe and CoCrSb are performed. The calculations reveal that CoCrTe and CoCrSb at their equilibrium lattice constants are half-metallic ferromagnets with half-metallic gaps of 0.28 and 0.22 eV and total magnetic moments of 3.00 and 2.00 B per formula unit, respectively. The calculated integer total magnetic moments (in B) are consistent with the Slater-Pauling rule, Mt = Zt-18, where Zt denotes the total number of valence electrons and Mt means the total magnetic moment (in B) per formula unit. Moreover, the spin moment of the Cr atom is obviously larger than those of the Co, Te, and Sb atoms. Co, Te and Sb are all antiferromagnetically coupled to Cr for CoCrTe and CoCrSb. The electronic structures of CoCrTe and CoCrSb are also calculated as their lattice constants change from -13% to +13% relative to the equilibrium lattice constant. The calculated results indicate that CoCrTe and CoCrSb can maintain their half-metallicities and retain their total magnetic moments of 3.00 and 2.00 B per formula unit even as their lattice constants change from -11.4% to 9.0% and from -11.2% to 2.0%, respectively. The semi-Heusler alloys CoCrTe and CoCrSb should be useful in spintronics and other applications.
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Keywords:
- first principle /
- half metal /
- electronic structure /
- magnetism
[1] de Groot R A, Mueller F M, van Engen P G, Buschow K H J 1983 Phys. Rev. Lett. 50 2024
[2] Yanase A, Siratori K 1984 J. Phys. Soc. Jpn. 53 312
[3] Schwarz K 1986 J. Phys. F: Met. Phys. 16 L211
[4] Galanakis I, Mavropoulos P 2003 Phys. Rev. B 67 104417
[5] Yao K L, Gao G Y, Liu Z L, Zhu L 2005 Solid State Commun. 133 301
[6] Xie W H, Xu Y Q, Liu B G, Pettifor D G 2003 Phys. Rev. Lett. 91 037204
[7] Yao Z, Zhang Y S, Yao K L 2012 Appl. Phys. Lett. 101 062402
[8] Zhang M, Dai X, Hu H, Liu G, Cui Y, Liu Z, Chen J, Wang J, Wu G 2003 J. Phys. Condens. Matter 15 7891
[9] Galanakis I, Mavropoulos P 2007 J. Phys.: Condens. Matter 19 315213
[10] Picizzio S, Continenza A, Freeman A J 2002 Phys. Rev. B 66 094421
[11] Droghetti A, Baadji N, Sanvito S 2009 Phys. Rev. B 80 235310
[12] Gao G Y, Yao K L 2012 J. Appl. Phys. 111 113703
[13] Soeya S, Hayakawa J, Takahashi H, Ito K, Yamamoto C, Kida A, Asano H, Matsui M 2002 Appl. Phys. Lett. 80 823
[14] Watts S M, Wirth S, von Molnar S, Barry A, Coey J M D 2000 Phys. Rev. B 61 9621
[15] Soulen Jr. R J, Byers J M, Osofsky M S, Nadgorny B, Ambrose T, Cheng S F, Broussard P R, Tanaka C T, Nowak J, Moodera J S, Barry A, Coey J M D 1998 Science 282 85
[16] Kato H, Okuda T, Okimoto Y, Tomioka Y, Takenoya Y, Ohkubo A, Kawasaki M, Tokuraa Y 2002 Appl. Phys. Lett. 81 328
[17] Zhao J J, Qi X, Liu E K, Zhu W, Qian J F, Li G J, Wang W H, Wu G H 2011 Acta Phys. Sin. 60 047108 (in Chinese) [赵晶晶, 祁欣, 刘恩克, 朱伟, 钱金凤, 李贵江, 王文洪, 吴光恒 2011 60 047108]
[18] Sakuraba Y, Hattori M, Oogane M, Ando Y, Kato H, Sakuma A, Miyazaki T, Kubota H 2006 Appl. Phys. Lett. 88 192508
[19] Wolf S A, Awschalom D D, Buhrman R A, Daughton J M, von Molnar S, Roukes M L, Chtchel-kanova A Y, Treger D M 2001 Science 294 1488
[20] Webster P J, Ziebeck K R A 1988 Alloys and Compounds of d-Elements with Main Group Elements (Berlin: Springer) pp75-184
[21] Ziebeck K R A, Neumann K U 2001 Magnetic Properties of Metals (Berlin: Springer) pp64-414
[22] Chen J, Gao G Y, Yao K L, Song M H 2011 J. Alloys Compd. 509 10172
[23] Zhang M, Dai X, Hu H, Liu G, Cui Y, Liu Z, Chen J, Wang J, Wu G 2003 J. Phys. Condens. Matter 15 7891
[24] Zhang M, Liu Z H, Hu H N, Liu G D, Cui Y T, Wu G H, Bruck E, de Boer F R, Li Y X 2004 J. Appl. Phys. 95 7219
[25] Kubler J 1984 Physica B, C 127 257
[26] de Groot R A, van der Kraan A M, Buschow K H J 1986 J. Magn. Magn. Mater. 61 330
[27] Blaha P, Schwarz K, Madsen G K H, Kvasnicka D, Luitz J 1990 Comput. Phys. Commun. 59 399
[28] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865
[29] Otto M J, van Woerden R A M, van der Valk P J, Wijngaard J, van Bruggen C F, Haas C, Buschow K H J 1989 J. Phys. Condens. Matter 1 2341
[30] Helmholdt R B, de Groot R A, Mueller F M, van Engen P G, Buschow K H J 1984 J. Magn. Magn. Mater. 43 249
[31] Galanakis I, Dederichs P H, Papanikolaou N 2002 Phys. Rev. B 66 134428
[32] Block T, Carey M J, Gurney B A, Jepsen O 2004 Phys. Rev. B 70 205114
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[1] de Groot R A, Mueller F M, van Engen P G, Buschow K H J 1983 Phys. Rev. Lett. 50 2024
[2] Yanase A, Siratori K 1984 J. Phys. Soc. Jpn. 53 312
[3] Schwarz K 1986 J. Phys. F: Met. Phys. 16 L211
[4] Galanakis I, Mavropoulos P 2003 Phys. Rev. B 67 104417
[5] Yao K L, Gao G Y, Liu Z L, Zhu L 2005 Solid State Commun. 133 301
[6] Xie W H, Xu Y Q, Liu B G, Pettifor D G 2003 Phys. Rev. Lett. 91 037204
[7] Yao Z, Zhang Y S, Yao K L 2012 Appl. Phys. Lett. 101 062402
[8] Zhang M, Dai X, Hu H, Liu G, Cui Y, Liu Z, Chen J, Wang J, Wu G 2003 J. Phys. Condens. Matter 15 7891
[9] Galanakis I, Mavropoulos P 2007 J. Phys.: Condens. Matter 19 315213
[10] Picizzio S, Continenza A, Freeman A J 2002 Phys. Rev. B 66 094421
[11] Droghetti A, Baadji N, Sanvito S 2009 Phys. Rev. B 80 235310
[12] Gao G Y, Yao K L 2012 J. Appl. Phys. 111 113703
[13] Soeya S, Hayakawa J, Takahashi H, Ito K, Yamamoto C, Kida A, Asano H, Matsui M 2002 Appl. Phys. Lett. 80 823
[14] Watts S M, Wirth S, von Molnar S, Barry A, Coey J M D 2000 Phys. Rev. B 61 9621
[15] Soulen Jr. R J, Byers J M, Osofsky M S, Nadgorny B, Ambrose T, Cheng S F, Broussard P R, Tanaka C T, Nowak J, Moodera J S, Barry A, Coey J M D 1998 Science 282 85
[16] Kato H, Okuda T, Okimoto Y, Tomioka Y, Takenoya Y, Ohkubo A, Kawasaki M, Tokuraa Y 2002 Appl. Phys. Lett. 81 328
[17] Zhao J J, Qi X, Liu E K, Zhu W, Qian J F, Li G J, Wang W H, Wu G H 2011 Acta Phys. Sin. 60 047108 (in Chinese) [赵晶晶, 祁欣, 刘恩克, 朱伟, 钱金凤, 李贵江, 王文洪, 吴光恒 2011 60 047108]
[18] Sakuraba Y, Hattori M, Oogane M, Ando Y, Kato H, Sakuma A, Miyazaki T, Kubota H 2006 Appl. Phys. Lett. 88 192508
[19] Wolf S A, Awschalom D D, Buhrman R A, Daughton J M, von Molnar S, Roukes M L, Chtchel-kanova A Y, Treger D M 2001 Science 294 1488
[20] Webster P J, Ziebeck K R A 1988 Alloys and Compounds of d-Elements with Main Group Elements (Berlin: Springer) pp75-184
[21] Ziebeck K R A, Neumann K U 2001 Magnetic Properties of Metals (Berlin: Springer) pp64-414
[22] Chen J, Gao G Y, Yao K L, Song M H 2011 J. Alloys Compd. 509 10172
[23] Zhang M, Dai X, Hu H, Liu G, Cui Y, Liu Z, Chen J, Wang J, Wu G 2003 J. Phys. Condens. Matter 15 7891
[24] Zhang M, Liu Z H, Hu H N, Liu G D, Cui Y T, Wu G H, Bruck E, de Boer F R, Li Y X 2004 J. Appl. Phys. 95 7219
[25] Kubler J 1984 Physica B, C 127 257
[26] de Groot R A, van der Kraan A M, Buschow K H J 1986 J. Magn. Magn. Mater. 61 330
[27] Blaha P, Schwarz K, Madsen G K H, Kvasnicka D, Luitz J 1990 Comput. Phys. Commun. 59 399
[28] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865
[29] Otto M J, van Woerden R A M, van der Valk P J, Wijngaard J, van Bruggen C F, Haas C, Buschow K H J 1989 J. Phys. Condens. Matter 1 2341
[30] Helmholdt R B, de Groot R A, Mueller F M, van Engen P G, Buschow K H J 1984 J. Magn. Magn. Mater. 43 249
[31] Galanakis I, Dederichs P H, Papanikolaou N 2002 Phys. Rev. B 66 134428
[32] Block T, Carey M J, Gurney B A, Jepsen O 2004 Phys. Rev. B 70 205114
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