GdN光学带隙的铁磁红移
Ferromagnetic redshift of the optical gap in GdN
摘要：
我们报告测量的光学带隙的GdN膜在温度从300至6K，覆盖了顺磁和铁磁相。在居里温度以下，顺磁相带隙为1.31eV，自旋分裂带隙红移到0.9eV。顺磁带隙比早期实验所建议的要大，并且允许我们改进（LSDA+U）计算的能带结构。在铁磁基态的完全平移对称下计算了能带结构，将顺磁态带隙指定为铁磁态中多数自旋带隙和少数自旋带隙的平均值。这一过程已经通过一个32原子随机自旋的超原胞的能带结构得到了进一步的验证。在仅拟合顺磁带隙之后，通过在X点处的直接跃迁，精确的能带结构再现了我们在两个相中测量的带隙。
英文摘要：
We report measurements of the optical gap in a GdN film at temperatures from 300 to 6K, covering both the paramagnetic and ferromagnetic phases. The gap is 1.31eV in the paramagnetic phase and red-shifts to 0.9eV in the spin-split bands below the Curie temperature. The paramagnetic gap is larger than was suggested by very early experiments, and has permitted us to refine a (LSDA+U)-computed band structure. The band structure was computed in the full translation symmetry of the ferromagnetic ground state, assigning the paramagnetic-state gap as the average of the majority- and minority-spin gaps in the ferromagnetic state. That procedure has been further tested by a band structure in a 32-atom supercell with randomly-oriented spins. After fitting only the paramagnetic gap the refined band structure then reproduces our measured gaps in both phases by direct transitions at the X point.
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