The electronic density of states, spin- splittings and atomic magnetic moments of the six- member ring N2C4 cluster with folding configuration in DNA bases have been studied by spin-polarized MS-Xα method. The results showed that there are at least four metastable states near the ground state level ?7.01635×103 eV. Those metastable states found in the calculation are at the levels ?7.01626× 103, ?7.01616×103, ?7.01606×103 and ?7.01597×103 eV, respectively. The electronic structures of those states were found to differ from each other. Therefore, they have different characteristics. The cluster exhib-its metal properties and has a weak antiferromag-netism in the ground state, while it shows ferrimag-netism and half-metal properties in the first metasta-ble state. The distribution of the electronic density of states of the six-member ring N2C4 cluster is very similar to that of some diluted magnetic semicon-ductors near the Fermi surface.
WANG Yongjuan LI Hua DONG Jianmin ZHANG Cha'ngwen PAN Fengchun
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 2e site. The calculated results for the Sm5Co28Ti6 cluster may lead to a better understanding of why SmCo7-xTix is stable phase. Since the negative interaction of 2e 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.
ZHANG Changwen1, LI Hua1, DONG Jianmin1, GUO Yongquan2 & LI Wei2 1. School of Physics and Microelectronics, Shandong University, Jinan 250100, 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 2e 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.
ZHANG Changwen 1 , LI Hua 1 , DONG Jianmin 1 , WANG Yongjuan 1 , PAN Fengchun 1 , ZHANG Jian 1 , GUO Yongquan 2 & LI Wei 2 1. School of Physics and Microelectronics, Shandong University, Jinan 250100, China
