Spin-Polarized Energy Bands in Eu Chalcogenides by the Augmented-Plane-Wave Method
Spin-Polarized Energy Bands in Eu Chalcogenides by the Augmented-Plane-Wave Method
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采用增强平面波法研究 Eu 硫属化物中的自旋极化能带
DOI：
10.1103/physrevb.1.4589
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发表时间：
1970
影响因子：
3.7
通讯作者：
S. Cho
中科院分区：
文献类型：
--
作者：
S. Cho
用增强平面波（APW）方法研究了Eu硫族化合物的自旋极化能带。4f波段的位置对所用的交换势极为敏感。一个减少的交换参数为3 - 4的磁性Eu 2+离子产生适当的能隙和相对f带的位置EuO，EuS，和EuSe。我们得到f（↑）带宽约为0.5 eV，上下自旋f带间距约为6 eV。我们还获得了约2 eV的阴离子p带宽，这几乎是恒定的Eu硫属化物。计算的态密度与光电发射数据定性一致，除了具有约1.5 eV的大带宽的4 f（↑）带的实验态密度。这种差异的可能原因是4f电子与声子和电子的多次散射，或与Eu 3+离子的复合。观察到的吸收边红移是由于最低导带X3的自旋极化交换分裂Δ Eex。Gd金属和Eu硫属化物的估计Δ E ex值为0.4-0.5 eV。Eu和Gd金属中的f（↑）带预计位于费米能级以下3 eV以内。讨论了高能反射率数据、有效质量、可能的传导机制和APW电荷分析。
Spin-polarized energy bands in the Eu chalcogenides have been obtained by the augmented-plane-wave (APW) method. The 4 f band positions are extremely sensitive to the exchange potential used. A reduced exchange parameter of 3 4 for the magnetic Eu 2+ ions has produced proper energy gaps and relative f band positions for EuO, EuS, and EuSe. We have obtained the f (↑) bandwidth as about 0.5 eV and the up-and down-spin f band separation as about 6 eV. We have also obtained anion p bandwidths of about 2 eV which are almost constant for the Eu chalcogenides. The calculated density of states agrees qualitatively with photoemission data, except for the experimental density of states of the 4 f (↑) band which has a large bandwidth of about 1.5 eV. The probable causes of this discrepancy are multiple scattering of the 4 f electrons with phonons and electrons, or recombinations with Eu 3+ ions. The observed absorption-edge red shifts are due to the spin-polarized exchange splitting Δ E ex of the lowest conduction band X 3. Estimated Δ E ex values are 0.4-0.5 eV for Gd metal and Eu chalcogenides. The f (↑) bands in Eu and Gd metals are expected to be located within 3 eV below the Fermi level. The high-energy reflectivity data, effective masses, possible conduction mechanism, and APW charge analysis have been discussed.