(CoMn)_n(n=1～5)合金团簇的结构和磁性

Structure and Magnetism of (CoMn)_n(n=1-5) Alloy Clusters

采用密度泛函理论中的局域自旋密度近似和广义梯度近似对(CoMn)n(n=1～5)团簇的几何构型进行优化、能量、频率和磁性计算,确定了团簇的基态,对其基态的磁性和电子结构进行了系统研究,并与相对应的一元团簇进行了结构和磁性比较.研究表明,两种方法确定的基态构型基本一致,当n=1～4时,等比CoMn二元合金团簇的几何形状仍与一元团簇相同;(CoMn)3和(CoMn)4团簇出现了磁性双稳态,显示铁磁性和反铁磁性耦合;二元CoMn合金团簇中Co、Mn原子磁性仍能保持一元Co、Mn团簇基态的磁性.

All geometry structures of （CoMn） n （ n = 1 - 5 ） clusters were optimized, and the energy, frequence and magnetism of （ CoMn ） n （ n = 1 - 5 ） clusters were calculated by using the local spin density approximation and generalized gradient approximation of density functional theory. The same ground state structures of CoMn alloy clusters were confirmed in two methods, and magnetism of CoMn alloy ground state clusters was studied systemically. In order to understand structure and magnetism of CoMn alloy clusters better, Co2n（n = 1 -5） and Mn2n（n = 1 -5） clusters were calculated by the same method as alloy clusters, whose ground state structure and magnetism were confirmed. Moreover, the ground state structure and magnetism of clusters with the corresponding CoMn alloy clusters was compared. Results indicated that for （CoMn）n（n = 1 -4） clusters, geometry structures of CoMn alloy clusters are the same as the corresponding pure clusters still, （CoMn）3 and （CoMn）4 exhibit magnetic bistability, show ferromagnetic and anti-ferromagnetic coupling, local magnetic moment of Co, Mn atoms in CoMn alloy clusters almost preserves magnetism of pure clusters still.