钨基Heusler合金W_(2)YZ的电子结构与磁性

Electronic structures and magnetic properties of W-based Heusler alloys W_(2)YZ

采用第一性原理计算方法研究了钨基Heusler合金W_(2)YZ(Y=Mn,Fe,Co;Z=Si,Ge,Sn,Sb,Te)的电子结构和磁学性质,并对不同晶体结构L2_(1)型和XA型下的15种W_(2)YZ合金进行晶体结构优化,结果表明,W_(2)YZ系列合金均具有有序的Hg_(2)CuTi型立方晶体结构,其中W_(2)CoTe合金具有最低的总能量,结构更稳定。电子结构计算结果表明,该系列Heusler合金均表现为金属特征,不显示半金属或半导体特性。其中9种合金的总磁矩与总价电子数的关系符合M_(t)=Z_(t)-24的Slater-Pauling规则,而W_(2)MnSb,W_(2)FeSn,W_(2)FeSb,W_(2)FeTe,W_(2)CoSb和W_(2)CoTe这6种合金的磁矩稍偏离直线M_(t)=Z_(t)-24。

The electronic structures and magnetic properties of tungsten-based Heusler alloys W_(2) YZ(Y=Mn,Fe,Co;Z=Si,Ge,Sn,Sb,Te)are studied using the first principle calculations.The crystal structures of 15 kinds of W_(2)YZ alloys with L2_(1) and XA were optimized.The results show that all W_(2)YZ alloys crystallize in ordered Hg_(2)CuTi-type cubic structure,and W_(2)CoTe has the lowest total energy and the most stable structure.The calculations of electronic structures indicated that all of the Heusler alloys investigated in the present work do not exhibit half-metallic or semi-conductor characteristics,and they are just ferromagnetic metals or nonmagnetic metals.Furthermore,we find that the relationships between the total magnetic moment and the total valence electron number in nine of the alloys satisfy the Slater-Pauling rule of M_(t)=Z_(t)-24,while the magnetic moments of the rest(W_(2)MnSb,W_(2)FeSn,W_(2)FeSb,W_(2)FeTe,W_(2)CoSb and W_(2)CoTe)deviate from the straight line slightly.