Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO3
Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO3
复制标题
DOI：
10.1002/adma.201908315
复制
发表时间：
2020-05
影响因子：
29.4
通讯作者：
K. Maruhashi;Kei S. Takahashi;M. Bahramy;S. Shimizu;R. Kurihara;A. Miyake;M. Tokunaga;Y. Tokura;M. Kawasaki
中科院分区：
文献类型：
--
作者：
K. Maruhashi;Kei S. Takahashi;M. Bahramy;S. Shimizu;R. Kurihara;A. Miyake;M. Tokunaga;Y. Tokura;M. Kawasaki
磁性半导体是理解量子输运现象的重要组成部分。为了探索这种微妙的，但从根本上重要的影响，这是至关重要的，以保持高载流子迁移率的磁矩的存在。然而，在实践中，磁化常常降低载流子迁移率。在此，显示EuTiO 3是磁性半导体的罕见实例，其可使用分子束外延来理想地生长以具有在2K下超过3000 cm 2 V-1 s-1的高载流子迁移率，同时固有地具有大磁化值，每分子式单位7 μB。这是证明通过测量的Shubnikov-de哈斯（SdH）振荡的铁磁状态的EuTiO 3膜与各种载流子密度。使用第一性原理计算，结果表明，观察到的SdH振荡真正起源于Ti 3d-t2 g态，由于它们在能量上接近带隙内Eu 4f带，因此它们是完全自旋极化的。这种交换耦合进一步显示出对Ti 3d-t2 g电子的有效质量和费米学具有深远的影响，表现为SdH振荡中的方向各向异性。这些发现表明EuTiO 3薄膜是一种理想的磁性半导体，为探索适合自旋电子应用的量子现象提供了肥沃的领域。
Magnetic semiconductors are a vital component in the understanding of quantum transport phenomena. To explore such delicate, yet fundamentally important, effects, it is crucial to maintain a high carrier mobility in the presence of magnetic moments. In practice, however, magnetization often diminishes the carrier mobility. Here, it is shown that EuTiO3 is a rare example of a magnetic semiconductor that can be desirably grown using the molecular beam epitaxy to possess a high carrier mobility exceeding 3000 cm2 V−1 s−1 at 2 K, while intrinsically hosting a large magnetization value, 7 μB per formula unit. This is demonstrated by measuring the Shubnikov–de Haas (SdH) oscillations in the ferromagnetic state of EuTiO3 films with various carrier densities. Using first‐principles calculations, it is shown that the observed SdH oscillations originate genuinely from Ti 3d‐t2g states which are fully spin‐polarized due to their energetical proximity to the in‐gap Eu 4f bands. Such an exchange coupling is further shown to have a profound effect on the effective mass and fermiology of the Ti 3d‐t2g electrons, manifested by a directional anisotropy in the SdH oscillations. These findings suggest that EuTiO3 film is an ideal magnetic semiconductor, offering a fertile field to explore quantum phenomena suitable for spintronic applications.