Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Nat Commun. 2016 Dec 19;7:13810. doi: 10.1038/ncomms13810.
Large spin-splitting in the conduction band and valence band of ferromagnetic semiconductors, predicted by the influential mean-field Zener model and assumed in many spintronic device proposals, has never been observed in the mainstream p-type Mn-doped ferromagnetic semiconductors. Here, using tunnelling spectroscopy in Esaki-diode structures, we report the observation of such a large spontaneous spin-splitting energy (31.7-50 meV) in the conduction band bottom of n-type ferromagnetic semiconductor (In,Fe)As, which is surprising considering the very weak s-d exchange interaction reported in several zinc-blende type semiconductors. The mean-field Zener model also fails to explain consistently the ferromagnetism and the spin-splitting energy of (In,Fe)As, because we found that the Curie temperature values calculated using the observed spin-splitting energies are much lower than the experimental ones by a factor of 400. These results urge the need for a more sophisticated theory of ferromagnetic semiconductors.
在铁磁半导体的导带和价带中存在大的自旋劈裂，这是由有影响力的平均场齐纳模型预测的，并且在许多自旋电子器件的提案中被假设，但在主流的 p 型 Mn 掺杂铁磁半导体中从未观察到。在这里，我们使用隧道谱学在 Esaki 二极管结构中，报告了在 n 型铁磁半导体（In，Fe）As 的导带底部观察到如此大的自发自旋劈裂能（31.7-50meV），这令人惊讶，考虑到在几种闪锌矿型半导体中报道的非常弱的 s-d 交换相互作用。平均场齐纳模型也不能一致地解释（In，Fe）As 的铁磁性和自旋劈裂能，因为我们发现，使用观察到的自旋劈裂能计算的居里温度值比实验值低 400 倍。这些结果促使人们需要一种更复杂的铁磁半导体理论。
