Tailoring the electronic structure of half-metallic Heusler alloys
Tailoring the electronic structure of half-metallic Heusler alloys
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DOI：
10.1103/physrevb.80.144405
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发表时间：
2009-10-01
影响因子：
3.7
通讯作者：
Elmers, H. J.
中科院分区：
文献类型：
--
作者：
Klaer, P.;Kallmayer, M.;Elmers, H. J.
利用圆二色性X射线吸收光谱（XMCD）研究了多晶Co（2）TiZ（Z=Si，Ge，Sn，Sb），Co2 MnxTi（1-x）Si和Co2 MnGa（1-x）Gex Heusler合金的元素特异磁矩和自旋分辨空占态密度（DOS）。我们发现一个小的（3亩（B））Mn矩取向平行于Co矩约1亩（B）每个原子在研究的化合物。与x = 0或x = 1的相应三元化合物相比，四元化合物的轨道磁矩增加。从XMCD数据中提取了Co原子上未占据的自旋分辨部分DOS。在Co2 TiSi、Co2 TiGe和Co2 TiSn的情况下，Co少数态密度在E-F上方0.5 eV处显示出最大值，在EF处显示出非常低的值，与半金属铁磁性的预期一致。相比之下，Co2 TiSb在费米能级处显示出像普通金属一样的大的少数DOS。在Co2 TiSi中Mn取代Ti使少数DOS最大值相对于费米能从0.5 eV移动到0.9 eV。对于系列Co2 MnGa 1-xGex，我们观察到的少数DOS的最大值从0.7 eV的x = 1到1.0 eV的x = 0，表明半金属铁磁性的整个系列的逐渐移位。我们的研究结果，揭示了磁矩的分布和费米能的相对位置作为价电子数的函数，证实了预测的可能性定制的少数带隙使用取代季Heusler化合物。这些结果对于理解复杂金属间化合物的电子结构具有重要意义。
We investigated element-specific magnetic moments and the spin-resolved unoccupied density of states (DOS) of polycrystalline Co(2)TiZ (Z=Si, Ge, Sn, Sb), Co2MnxTi1-xSi and Co2MnGa1-xGex Heusler alloys using circular dichroism in x-ray absorption spectroscopy (XMCD). We find a small (3 mu(B)) Mn moment oriented parallel to the Co moment of approximately 1 mu(B) per atom in the investigated compounds. Orbital magnetic moments are increased for quaternary compounds compared to the corresponding ternary compounds with x = 0 or x = 1. The unoccupied spin-resolved partial DOS at the Co atom was extracted from the XMCD data. In the case of Co2TiSi, Co2TiGe, and Co2TiSn, the Co minority DOS reveals a maximum at 0.5 eV above E-F and very low values at EF in agreement with the expectation for half-metallic ferromagnetism. In contrast, Co2TiSb shows a large minority DOS at the Fermi energy like a normal metal. A substitution of Ti by Mn in Co2TiSi shifts the minority DOS maximum from 0.5 to 0.9 eV with respect to the Fermi energy. For the series Co2MnGa1-xGex we observe a gradual shift of the minority DOS maximum from 0.7 eV for x = 1 to 1.0 eV for x = 0, indicating half-metallic ferromagnetism for the whole series. Our results, revealing the distribution of magnetic moments and the relative position of the Fermi energy as a function of the number of valence electrons, confirm the predicted possibility of tailoring the minority band gap using substitutional quaternary Heusler compounds. The results maybe of general importance for the understanding of the electronic structures in complex intermetallic compounds.