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Electronic structure and magnetic properties of SmCo7-xTix

Science China(physics,Mechanics & Astronomy) 2006年第1期49卷 38-45页

作者： zhang changwen1, li hua1,{2., guo yongquan2.& li wei2.1. school of physics and microelectronics, shandong university, jinan 2.0100, China 2. Institute of Functional Materials, Central Iron and Steel Research Institute, Beijing 100081, China 1. school of physics and{2. Shandong University Jinan 250100 China 2. Institute of Functional Materials Central Iron and Steel Research Institute Beijing 100081 China

Electronic structure of SmCo7-xTix alloy has been studied by means of the spin-polarized MS-Xα method. It is shown that a few of electrons are transferred to Sm(5d) orbital due to orbital hybridization between Sm and Co atoms. The exchange interaction between 5d-3d electrons is stronger, which is the main reason resulting in the long-range ferromagnetic order between Co and Sm atoms. The Curie temperature of SmCo7-xTix is generally lower than that of pure Co metal, which may be explained by the weaker aver- age of coupling strength between Co sites due to some negative exchange couplings occurring mainly at 2. site. The calculated results for the Sm5Co2.Ti6 cluster may lead to a better understanding of why SmCo7-xTix is stable phase. Since the negative interaction of 2. sites weakens and the bonding at EF strengthens with increasing Ti concentration, which result in the decrease in the free energy of the alloy, the stable ferromagnetic order forms inside SmCo7-xTix. Considering the localization of 4f states and 5d moment arising from the orbital hybridization, the calculated moment is 9.47μB per formula unit that is in agreement with experiments.

关键词： electronic structure, spin polarization, atomic magnetic moment, exchange coupling, Curie temperature.

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Electronic structure and magnetic properties of metastable SmCo_(7) compound

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Science China(physics,Mechanics & Astronomy) 2005年第3期48卷 325-335页

作者： zhang changwen 1 , {2. hua 1 , dong {2. 1 , WANG Yongjuan 1 , PAN Fengchun 1 , zhang Jian 1 , guo yongquan 2.& {2. wei 2.1. {12. of physics and microelectronics, shandong university, jinan 2.0100, China 2. Institute of Functional Materials, Central Iron and Steel Research Institute, Beijing 100081, China 1. school of physics and{2. Shandong University 250100 Jinan China 2. Institute of Functional Materials Central Iron and Steel Research Institutes 100081 Beijing China

The electronic density of states, spin-splittings and atomic magnetic moments of SmCo 7 compound have been studied using spin-polarized MS-Xα method. The results show that a few of electrons are transferred to Sm(5d 0 ) orbital because of orbital hybridization between Sm and Co atoms in the compound. The exchange interactions between 3d and 5d electrons lead to the magnetic coupling between Sm and Co, and therefore, result in the long-range ferromagnetic order inside the SmCo 7 compound. There are negative exchange couplings occurring at some levels, which weakens the strength of average coupling around Co lattice. So, the Curie temperature and Co-moment of SmCo 7 decrease distinctly compared with pure Co. Compared with SmCo 5 compound, the disordered substitution of Co-Co “dumbbell-atom” pairs for Sm changes the local environment of Co lattice, which makes the 2. site bear negative magnetic moment. The strength of hybridization near Fermi level weakens and the free energy of the compound increases obviously. Thus, SmCo 7 is a metastable compound at room temperature. Considering the localization of 4f electrons and a few of 5d electrons arising from the orbital hybridization, the magnetic moment of Sm atom will be 1.61μ B in SmCo 7 compound, which is in agreement with the experimental values of Sm 3+ ion- moment and Sm atom-moment in metals.

关键词： electronic structure, spin polarization, atomic magnetic moment, exchange coupling, Curie temperature.

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Analysis of Electronic Structures for SmCo5 Compound

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Journal of Rare Earths 2004年第Z1期22卷 103-106页

作者： zhang changwen {2. hua guo {2. {2. wei dong jianmin school of physics and{2. Shandong University Jinan 250100 China School of physics and Microelectronics Shandong University Jinan 250100 China Institute of Functional Materials Central Iron &Steel Research Institute Beijing 100081 China Institute of Functional Materials Central Iron &Steel Research Institute Beijing 100081 China School of physics and Microelectronics Shandong University Jinan 250100 China

The spin-polarized MS-Xα method is employed to study the electronic structure and the magnetic property of the SmCo5 *** to the calculated results, the magnetic moment per Sm is 1.2.μB in the SmCo5 compound, which agrees with that of *** analyzed result reveals that some negative exchange couplings occurring at six energy levels induce the distinct decrease of Curie temperature and the magnetic moment per *** valence electron numbers of 2.48, which are derived from the orbital hybridization from s, p, d and f functions between Sm and Co atoms, are transferred to Sm(5d0) ***, the exchange interactions between 3d ～ 5d electrons lead to the magnetic coupling between Sm and Co, which results in the long-range ferromagnetic-order inside the SmCo5 compound.

关键词： electronic structure atomic magnetic moment exchange coupling Curie temperature

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